Home range and activity budget in the Falkland Steamer Duck (Tachyeres brachypterus)

Alix M I Kristiansen; Alastair MM Baylis; Sébastien AP Dupray; Luc Lens; Heather Q Mathews; Lucy J Mitchell; John P Y Arnould

doi:10.1371/journal.pone.0333302

. 2025 Oct 7;20(10):e0333302. doi: 10.1371/journal.pone.0333302

Home range and activity budget in the Falkland Steamer Duck (Tachyeres brachypterus)

Alix M I Kristiansen ^1,^2,^*, Alastair MM Baylis ³, Sébastien AP Dupray ⁴, Luc Lens ², Heather Q Mathews ¹, Lucy J Mitchell ², John P Y Arnould ¹

Editor: Lee W Cooper⁵

PMCID: PMC12503321 PMID: 41056300

Abstract

The Falkland Islands support globally important populations of seabirds and coastal birds, underscoring their value for international conservation efforts. However, substantial knowledge gaps impede the development of coherent species management plans. This study focused on the endemic Falkland Steamer Duck, a territorial waterfowl only found around the archipelago, which has remained largely understudied and lacks fundamental ecological information critical to its conservation. To estimate home range sizes, habitat use, and activity budgets, we deployed GPS devices on 29 ducks from two locations (Bleaker Island and Stanley Harbour). Daily travel distances increased with proximity to ponds, kelp beds, and human infrastructures, within each duck’s home range. Absolute area, but not proportion of, kelp significantly influenced home and core range. Patrolling males and incubating females spent less time travelling (respectively 31.4 ± 2.5% and10.3 ± 0.9%), with females spending the most time on land (70.0 ± 2.4%) in line with their breeding role. Foraging time increased closer to kelp, and within larger areas of kelp, as well as closer to human infrastructure. Kelp beds are present in coastal waters all over the archipelago and, consequently, likely influence the distribution and density of Falkland Steamer Ducks. Therefore, any changes in their absolute area are expected to negatively impact the species. Preserving the kelp beds would therefore ensure a stronger resilience of the Falkland Steamer Duck in the context of ongoing climate change.

Introduction

Understanding how much space a species needs, the habitat type it uses, and its intra- and inter-specific interactions is central to understanding its ecology. Estimation of home range, the geographic space which allows the individual to feed, mate and raise its young [1], is a fundamental tool for conservation and decision-making, and has been used for example, to design Marine Protected Areas [2,3] or to define Important Bird Areas [4,5]. These estimates are particularly crucial for islands, which hold a higher concentration of often endemic species of limited distribution than the mainland [6]. Additional constraints to endemic species success, such as competition with invasive species and climate change [7,8], often result in data limitations hindering their conservation.

Understanding how a species’ home range is shaped, and what resources and environmental factors define it, can facilitate better, more informed responses, should conditions, and consequently the species’ population status, change [9]. For territorial species, their defended range is most likely a smaller component of their overall home range, and here they rely on resources that are of relatively constant value across the breeding period [10]. Territories of marine waterfowl encompass both marine and terrestrial habitats, reflecting their diverse needs. Most studied species are found in North America and Europe [11–13], and are migrants for which breeding and/or wintering grounds have been well described.

In contrast, relatively little is known of the marine waterfowl of South America and the Falkland Islands [14,15]. The Falkland Steamer Duck (Tachyeres brachypterus) is a member of the genus Tachyeres, found solely in South America and the Falkland Islands [16,17] (Fig 1). The genus comprises one flying species (T. patachonicus King, 1831) and three flightless species (T. pteneres (Forster, 1844), T. leucocephalus (Thompson, 1981), T. brachypterus (Latham, 1790)). Individuals of this genus form apparently long-term pair-bonds [18], guarding well-defended territories year-round [19], with incubation conducted solely by females [20] and the territory revolving around her [21]. The Falkland Steamer Duck, one of only two endemic bird and mammal species on the Falkland Islands, along with Cobb’s wren (Troglodytes cobbi) , is ubiquitous along the coastlines. However, its current population size is unknown [22], and there is presently limited information on its movement or the factors that might influence their territory size [23]. Despite the lack of detailed information, Falkland Steamer Ducks are currently classified as “Least concern” by the IUCN [24].

Fig 1 — The coastline was represented by a shapefile provided by SAERI (FK -UKHO-414) and the South America polygon originates from rnaturalearth package.

Studies on Steamer ducks in South America thus far comprise information on both territory defence and nesting behaviour. In Argentina, the White-headed Steamer Ducks (T. leucocephalus) were found to select nest sites in areas with high proportions of shrub vegetation [25]. On the Falkland Islands, on the south bank of Stanley Harbour, one pair of Falkland Steamer Ducks had a nest around 0.8 km away from the shore, on the north side of the harbour [26], comprising a high proportion of shrub vegetation and ferns. The same study also reported two pairs nesting in tussac, suggesting similar nesting habitat as T. leucocephalus. Additionally, Falkland Steamer Ducks are believed to rely on access to freshwater [27], as a potential way to compensate for any salt stress linked to its diet [28].

The coastal ecosystem of the Falkland Islands presents a wasp-waist structure [29]. This type of ecosystem, instead of being either bottom-up or top-down driven, depends on its intermediate trophic level species [30]. A main feature of the Falkland Islands nearshore coastal ecosystem is the kelp beds, mainly of Macrocystis pyrifera [31]. This macroalgae provides several ecosystem services, hosts a diversity of species, dominated by Gastropods, Ascidiacea and Demospongia [32]. In a previous Falkland Steamer Duck study, individuals were consistently observed less than 100 m away from surface-visible kelp beds, suggesting the importance of kelp beds to Falkland Steamer Ducks [27].

The scant, disparate pieces of information available on the Falkland Steamer Duck and its ecology leave many questions unanswered. Therefore, we sought to undertake a more detailed ecological tracking study to collect high resolution data on their movements and behaviour. Further, to identify key factors influencing Falkland Steamer Duck behaviour, along with collected GPS data, we recorded a number of variables that we believed to be environmentally relevant based on literature and field observations. Kelp beds and ponds were chosen as they are considered important resources for Falkland Steamer Ducks [19,26,27] and, thus, a good predictor of foraging habitat [18,19]. Human disturbance has been shown to affect anatid species [33] and was therefore also included in the analyses in the form of measured linear distances from bird GPS locations to settlements and roads. We hypothesised that (i) distance to kelp beds, ponds and human structures (i.e., roads and settlements) influences daily activity budget (i.e., distance travelled per day and proportion of time spent foraging); (ii) absolute area of kelp cover and proportional area of kelp beds constrains home and core range size; and (iii) breeding status, sex and study site impact time spent on land, home and core range size and daily activity budget (behaviour varies with breeding stage and habitat quality).

Methods

Study site and animal handling procedures

The study was conducted around Stanley Harbour and Bleaker Island, East Falkland (Fig 1). Stanley Harbour is a sheltered natural embayment which hosts the city of Stanley (human population: 2,974 – Fig 1). The terrestrial vegetation differs between the urbanised areas (gardens, including introduced tree species) and the embayment coastline (mix of fern beds and shrub [34]). The coastline is comprised of stony beaches, with the exception of the sandy beaches found in York Bay and Surf Bay [15]. The density of Falkland Steamer Ducks was estimated to be of 7.7 pairs·km^-1 along the coastline of Stanley Harbour and its surroundings (Fig 1, [35]). In contrast, Bleaker Island has a more diverse coastline, with a topography which varies between cliffs, coves with pebbly beaches, and a long (1.6 km) sand beach on the east side of the island. There is a small settlement on the island that hosts a variable population of 5−20 people, depending on the number of tourists. The density of breeding pairs of Falkland Steamer Ducks in the Bleaker Island study area was estimated to be 9.8 breeding pairs·km^-1 of coastline (Kristiansen et al in prep.).

Animal handling procedures were conducted under the approval of the Falkland Islands Government (Research Licence R25.2022). Data collection occurred during the austral summer breeding periods of 2022/23 and 2023/24. Adult individuals were captured using a noose pole while roosting on the beach and placed in a cloth bag for weighing using a spring scale (Salter, Bristol, UK, 5.00 ± 0.25 kg). The sex of individuals was determined based on plumage characteristics [36]. Breeding status was extracted from a concurrent breeding phenology survey, which ran from September 2023 to February 2024 (Kristiansen et al in prep.). Breeding status was divided into four categories: incubating females; male partners of incubating females (hereafter, patrolling male); chick-rearing individuals (both sexes); non-breeding individuals (both sexes; 29) and assigned for the GPS tracking period.

A GPS data logger (IgotU GT120B (14.9 g), G2S (14.4 g) or G6S (20.9 g), MobileAction, Taiwan) sealed in heat-shrink plastic (60 x 40 x 11 mm) was then attached to dorsal feathers between the scapula using waterproof tape (Tesa Tape® 4651, Beiesdorf, AG, Germany (Wilson et al. 1997)). The GPS data loggers were programmed to record locations at 2 min intervals. Individuals were then released at the point of capture and observed remotely to ensure they resumed normal behaviours. Handling procedures lasted <30 min. Data were downloaded every 1–2 d from the device in situ using a Bluetooth® connection onto a mobile data storage unit. Data on the movements of free-ranging Falkland Steamer Ducks comprising >1 d of records were obtained from a total of 29 individuals (21 males, 8 females – Table 1, Fig 2), during 2 breeding seasons (austral summer 2022–2023 and austral summer 2023–2024). Tracking duration varied between 1 and 43 d (16.9 ± 1.0 d). Of the 8 females, 5 were observed to be incubating, 2 were chick-rearing and 1 was assumed to have failed breeding. Three of the males were observed to be chick-rearing, 4 were captured while patrolling their territory alone but seen with a partner at other times (and, thus, presumed to be partnered with an incubating female), and the remainder were individuals of a pair that were assumed to have failed breeding or did not engage in breeding. No two individuals tagged originated from the same breeding pair.

Table 1. Summary table of travelled distances along the trajectory of movement, core and home range depending on sex and breeding status. All values represent the mean ± standard deviation. *: Home and core ranges were computed for 17 individuals: 3 females, 14 males; 8 non-breeding individuals, 6 chick-rearing individuals, 1 incubating female and 2 patrolling males.

		Weight (kg)	Mean distance (km.d^-1)	Maximum distance (km.d^-1)	Core range (ha)*	Home range (ha)^*
Sex	Female (n = 8)	3.66 ± 0.18	8.63 ± 0.64	12.16 ± 1.06	1.18 ± 0.62	8.17 ± 4.97
Sex	Male (n = 21)	4.68 ± 0.07	10.79 ± 0.61	14.03 ± 0.93	3.93 ± 1.08	21.76 ± 7.34
Breeding status	Incubating female (n = 5)	3.21 ± 0.010	8.52 ± 0.96	13.01 ± 1.49	2.42	17.97
	Patrolling male (n = 4)	4.78 ± 0.19	8.04 ± 0.04	12.22 ± 1.59	6.56 ± 1.65	39.17 ± 20.30
	Chick rearing (n = 7)	4.58 ± 0.22	10.35 ± 1.04	12.41 ± 1.41	2.55 ± 1.56	10.44 ± 6.01
	Non-breeding (n = 13)	4.78 ± 0.19	11.41 ± 0.75	14.70 ± 1.27	3.46 ± 1.51	21.28 ± 11.35

Open in a new tab

Fig 2 — Home and core ranges with sufficient data were coloured in black (males) and red (females) while nominal home and core ranges with insufficient data were coloured in light grey (males) and orange (females). Kelp beds were represented in beige.

Data analysis

All analyses were conducted in the R statistical environment (v. 4.4.2, R CoreTeam, 2018). Raw movement tracks were filtered to remove erroneous locations using a maximum travel speed of 38.6 km·h^-1, corresponding to steaming speed [37]. Movement tracks were then interpolated at 2 min intervals using the adehabitatLT package [38] and daily distances travelled (km) were calculated along the trajectory of movement.

Home and core ranges were estimated by analysing the collected GPS data with the biased-random bridge kernel method [39,40]. Firstly, to identify resident individuals for whom we had sufficient data to calculate the home range, we produced variograms using the ‘variogram’ function from the ctmm package. Individuals were considered resident when the variograms approached an asymptote [41]. Any individuals that did not reach or maintain an asymptote were not considered for home and core range analysis. We defined home range based on two levels of the Utilisation Distribution (UD) obtained via the biased-random bridge kernel method [39]. This method produces an occurrence distribution, rather than a true extrapolated home range, and represents a version of Brownian bridges [42] using the movement-based kernel density estimation. We estimated the wider home range (UD₉₅) and core range (UD₅₀), representing the area in which the individual can be found 95% and 50% of the tracked time. All metrics were extracted using ‘getverticeshr’ function from the adehabitatHR package and the obtained contours mapped using the ggplot2 package. To identify factors influencing the size of the core and wider home ranges, we ran, for each level, two linear regressions with either sex or breeding status, as well as proportion and absolute area of kelp, and study site, as fixed effects, and weighted by tracking duration, to account for differences among individuals in the length of time they were tracked.

To assess which factors influence daily distance travelled, we ran a Generalized Linear Mixed Model (GLMM; gaussian distribution, glmmTMB package), with fixed effects of breeding status, location, distance to kelp and to roads, and a random effect of individual.

Time spent on land was computed as the number of GPS locations on land. To identify factors influencing time spent on land, we used a GLMM (betabinomial family weighted by the total points at land and at sea), with breeding status, and study site as fixed effects and individual as a random effect.

From the GPS locations of each individual, three ecologically relevant statuses (resting, foraging and travelling) were determined using Hidden Markov Models. These models rely on an observable set of data (here the tracking data for each individual), to infer a non-observable state dependent on the distance and angle between subsequent points (step length, and turning angle) [43]. Using the moveHMM package [44], we defined the form of each state, which were then used to estimate the proportion (%) of time spent in each state. Resting is depicted as having the lowest step length and low turning angles. Commuting is best described by rapid movements, that is to say long step length and low turning angles. Whereas sharp turning angles and lower step lengths indicating more tortuous movements, indicative of exploration, represent foraging.

To identify factors influencing variation specifically in the proportion of time spent foraging per hour of the day, we ran a GLMM (beta-binomial distribution, weighted by total foraging points), with breeding status, location, distance to roads, settlements and kelp, as well as absolute kelp bed area as fixed effects, and individual as a random effect. The ‘nearest’ function in the terra package in R was used to compute all distances. Distance to infrastructure (a proxy for human disturbance) was calculated as the distance between the centre of a given home range or each GPS location and the nearest road and settlement separately. Similarly, distance to the kelp was computed as distance from the kelp polygons (source: FK-SAERI -284) to coast, for all models using this variable, except for the proportion of time spent foraging. Instead, distance was computed between each GPS location and the nearest kelp forest. The proportion of kelp was calculated as the size of the intersection between the polygons of kelp beds and either the core or home range. Kelp area was calculated as the absolute value of area of kelp present in either the core or home range. Maps were made using the coastline shapefile provided by SAERI (FK-UKHO-414) and the rnaturalearth package [45].

For all models, track duration was added as a weight when relevant, and fit was assessed by simulating residuals in the DHARMa package. For each model, we have also included a null model with no additional terms to provide a baseline output. Terms were dropped sequentially, and models were ranked by AIC (‘dredge’ function, MuMin package), with a minimum difference of ΔAIC = 4 [46]. If numerous candidate models were within ΔAIC = 4, we judged them to have equal support and performed model averaging (‘model.avg’ function, MuMin package). For each averaged model, the 95% confidence interval was calculated and effects that did not cross 0 were considered significant.

Results

After assessment of the individual variograms (see Methods, and S1/ S2), 17 individuals were kept for home and core range analysis. As this resulted in too few incubating females and patrolling males, we only compared changes in home and core ranges between chick-rearing and non-breeding individuals. Overall, mean home range size was 19.36 ± 6.19 ha. Mean core range size was 3.44 ± 0.92 ha. Daily travelled distances were computed along each individual’s trajectories. Falkland Steamer Ducks travelled on average 10.19 ± 0.50 km with a maximum of 13.52 ± 0.74 km and varied between breeding status (Table 1). In our preferred, lowest AIC model, all variables except status and proportion of kelp were retained for the home range analysis when status is considered (Table 2 and S1).

Table 2. Model estimates for each dependent variable in Table 1. * = model averaged estimates. The values represent the 95% interval. Bold numbers show significance. Light grey indicates variables not kept for the averaged modelling and dark grey not included in the modelling.

Model	Intercept	Sex (male)	Status (IF)	Status (PM)	Status (CR)	Study site (Stanley)	Area kelp	Percent kelp	Distance to kelp (km)	Distance to roads (km)	Distance to settlement (km)	Distance to ponds (km)
Distance travelled (km.d^-1)*	−0.84–4.21		−6.51 – −0.09	−7.65 – −1.46	−4.63–0.83	−0.05–5.75			0.0005–0.0141	0.0004 – 0.0007	0.0005 – 0.0029	1.42.10 ^-6 _– 3.30.10- ⁶
Home Range (95%) – sex*	1.20–2.78	−1.21–1.76				0.16–1.58	0.04–0.14	0.06–0.04
Home range (95%) – status	1.08 – 2.15					0.37–1.86	0.04–0.13
Core Range (50%) – sex*	−0.36–0.83	−0.92–1.61				0.41–1.58	0.30–1.16	−0.05–0.01
Core range (50%) – status *	−0.32–0.67				[NB] −0.36–0.94	−0.06–1.36	0.58–1.44	−0.04–0.01
Proportion time on land*	−1.44–0.09		0.65 – 3.23	−1.98 – 0.71	−1.06–1.21	−1.65–0.28
Proportion time foraging*	1.27–10.84	−0.59–0.56	0.04–1.09	−0.11–0.96	0.11–1.09	−9.42 – −1.26	50%: −1.30 – −0.33/ 95%: 0.05–0.22	50%: −0.03–0.04/ 95%: −0.05–0.00	−0.73–0.47	−0.0004 – −0.0001	−0.61 – −0.21

Open in a new tab

Home and core ranges

Size of core and home ranges were hypothesised to be influenced by sex/breeding status, study site, absolute area of kelp, proportion of kelp and distances to roads, settlements and ponds. Mean core range size was not significantly influenced by sex (P = 0.595) nor by breeding status (P = 0.377). Kelp cover was significantly influencing the size of both home (P _sex< 0.001; P _status = 0.001) and core range (P _sex= 0.001; P _status < 0.001)_, unlike the proportion of kelp present (home range: P _sex= 0.727, core range: P _sex= 0. 117; P _status = 0.377 –Fig 3). Study site was always significant, except when considering the core range between non-breeding and chick rearing individuals (Table 2 and Fig 3,Fig.4).

Daily travelled distances

Mean distance travelled was hypothesised to be influence by breeding status, study site and distance to kelp, roads, settlements and ponds. All considered variables were retained (Table 2 and Fig 3,Fig.4). Travelled distance significantly differed between breeding status, with incubating females (8.52 ± 0.96 km.d^-1) and patrolling males (8.04 ± 0.04 km.d^-1) travelling significantly less than non-breeding individuals (11.41 ± 0.75 km.d^-1; P = 0.004 and P = 0.044 respectively). Travelled distances also increased significantly with greater distances to kelp beds (P = 0.034) and to ponds (P < 0.001). Likewise, the greater the distance to roads and settlements, the more individuals travelled (P < 0.001 and P = 0.004 respectively).

Time spent on land

Proportion of time spent on land was hypothesised to be influenced by breeding status and study site. Similarly, all variables included in the analysis of time spent on land were retained (Table 2 and Fig 3,4). Time spent on land differed significantly between incubating females (70.00 ± 2.43% of recorded GPS points – P = 0.003) and the rest of the breeding categories (NB: 32.50 ± 1.73%; CR: 40.09 ± 2.70% and PM: 21.83 ± 2.73% of recorded GPS points– S 3). Incubating females exhibited two minimums in time spent on land: one between 5 and 7 AM and one between 6 and 7 PM (Fig 5). Chick-rearing individuals exhibited two declines in time spent on land around midnight, followed by a prolonged period between 1 AM to 11 AM during which they spent up to 63% of their time on land. A second minimum occurs between 12 AM and 4 PM. Non-breeding individuals showed a limited period on land, regardless of the time of the day. Patrolling males showed minimal land use around 9 AM, which increased to 42.5% at noon, followed by a gradual decrease until 8 PM. This was followed by a drop around midnight and a second peak at 4 AM, reaching a maximum of 45% before declining again. (Fig 5).

Fig 5 — Proportions were calculated as the number of GPS locations on land divided by the total number of GPS locations per individual. Black lines indicate error bars.

Time spent foraging

Time spent foraging was hypothesised to be influenced by breeding success, study site, absolute kelp cover and proportion of kelp cover in both the core and home ranges and distances to roads, settlements, kelp and ponds. Distance to ponds was the only variable not retained for the model averaging for time spent foraging. Individuals closer to roads (P = 0.010) and settlements (P < 0.001) spent significantly more time foraging. On the other hand, when considering the entire study sites, individual living in the area of Stanley Harbour spent significantly less time foraging (37.8 ± 0.98%) than those living on Bleaker Island (54.0 ± 1.25% - P = 0.010). The wider the absolute kelp area in the core range, the less time was spent foraging while the reverse was predicted for kelp cover in the home range. On the contrary, neither the distance to kelp beds (P = 0.667) nor the proportion of kelp beds influenced signifanlty at neither core (P = 0.823) nor home (P = 0.073) range level.

Collectively, individuals spent 21 ± 1.8% of their time travelling, 48 ± 2.8% foraging and 31 ± 2.6% resting (Fig 6). Incubating females (P = 0.036) and chick-rearing individuals (P = 0.015) spent significantly more time foraging than patrolling males (P = 0.123) when compared to non-breeding individuals. Sex did not have an effect, however (P = 0.96). Incubating females spent 45.64 ± 1.72% of their day foraging, chick-rearing individuals 55.93 ± 1.72%, patrolling males 43.72 ± 2.39% and non-breeding individuals 44.42 ± 1.40%.

Discussion

This study represents the first investigation into the movement ecology of Falkland Steamer Ducks, and more broadly of the Tachyeres genus, using high-resolution GPS tracking. Our results demonstrate that breeding status, study site, distance to ponds and kelp characteristics (i.e., kelp cover and distance to kelp beds) all significantly influence different facets of Falkland Steamer Duck movement ecology. In addition, human disturbance also played a significant role. Our findings establish a baseline for understanding the spatial ecology of Falkland Steamer Ducks and highlight the species’ potential role as a sentinel of environmental change.

Home and core ranges

Home range sizes were significantly larger at Stanley harbour than Bleaker Island. Those differences in size might reflect differences in habitat quality. All home and core range models highlight the importance of absolute kelp cover and not of the percentage of kelp cover in either the home or core range. This suggests that the size of both the home and core range may vary to maintain access to a sufficient level of kelp beds. A larger territory may reflect the breeding pair’s need to secure suitable kelp beds capable of providing adequate resources. Alternatively, differences in breeding pair density may play a role in territory size. For example, northern Bleaker Island supported a higher breeding pair density (9.8 pairs.km^-1) compared to Stanley (7.7 pairs.km^-1), which could reflect individuals occupying smaller, resource-rich territories (Kristiansen et al in prep.).

The proportion of kelp within the territory did not appear to influence either home or core range size, as opposed to absolute area of kelp. Several factors may explain this. First, territory size may vary to ensure access to a minimum threshold of absolute kelp cover. Once reached, the proportion of kelp becomes less relevant, as long as the kelp beds provide sufficient resources [47]. Second, Falkland Steamer Ducks may also rely on additional foraging resources beyond kelp beds. Individuals were frequently observed dabbling close to the shoreline [27], suggesting coastal nearshore habitat also provides access to prey resources. Further research into diet composition might shed light on the relative contribution of kelp-associated versus coastal food sources.

Daily travelled distances

Incubating females and patrolling males travelled less than non-breeders. Within the Tachyeres genus, only females undertake incubation [15,36], with the male assuming sole patrolling duties during this period [20]. During incubation, females rely on an easy access to high-quality resources to minimize time away from the nest, and mitigate declines in body condition associated with maintaining optimal nest temperature [48,49]. Meanwhile, patrolling males have been described as surveying the sea territory near the nest [50]. Hence, the movements of incubating pairs are restricted, when compared to non-breeders.

The finding that duckling-rearing individuals had similar mean and maximum distance travelled as non-breeders likely reflects parents not needing to be central place foragers as ducklings can self-feed in the presence of adults throughout their territory [18,51]. It may also result from the parents holding a territory, which requires defending regardless of the presence or not of ducklings. Anecdotally, a female with ducklings was seen joining her partner in a territorial fight, despite the potential negative effect of abandoning the brood (e.g., injury due to the fight, opportunities for flying predators).

Individuals travelled more when the distance to kelp and to ponds increased, potentially reflecting the need for territories to include feeding and resting areas but also access to freshwater. In diving sea ducks, drinking freshwater was thought to reduce salt stress and suggested salt stress as possible structuring factor when considering habitat quality [28]. In our study, tracked individuals walked inland solely to drink. Additionally, individuals travelled more when distance to roads and settlements increased. One hypothesis could be that territories away from human structures might present higher-quality habitats, where more individuals decide to establish their territories. Where there is a higher density of individuals, more time might be dedicated to territory defence, and neighbouring birds may have to travel further to access resources and avoid conflict. This could also help to explain the high individual variation, and high residual variation (i.e., unexplained differences), in daily distance travelled. Unfortunately, true density of neighbours was not identified for each tracked individual. In the future, these data should be collected, and the use of accelerometery data could also identify territorial displays, such as steaming and physical contact with intruding neighbours.

Time spent on land

Incubating females spent the most time on land, with minimums close to sunrise and sunset. More time spent on water at these times could translate a trade-off between the need to forage and the risk of nest predation by diurnal predation. A similar pattern was found for the Chubut Steamer Duck [50] and was hypothesised to represent a strategy to avoid nest predation from visual predators such as the Kelp Gull (Larus dominicanus), and the Striated caracara (Phalcoboenus australis).

All tagged parents had, at the time of the monitoring, young ducklings. Due to their downy plumage and lack of efficient insulation, ducklings present a limited waterproofness making them more prone to lose heat and unable to stay in water for extended periods of time [52]. As the ducklings grow older, their plumage retains less water, meaning they can retain their body heat, allowing them more time on water [53]. Hence, parents with young ducklings are more temporally constrained to shore than those with older ducklings, and non-breeding individuals [50] (Fig 5). Indeed, non-breeding individuals appear to be spending on average more than 60% of their time at sea, which could originate from the necessity to prevent intrusion from juveniles [15] or neighbours [26] through patrolling. This translates in the mean distance travelled per day. Both non-breeding and chick-rearing pairs are at a stage where they can defend their access to kelp. Non-breeding pairs only differ in their time spent on land since they are not constrained by a brood.

Patrolling males also spent most of their time at sea. During incubation, the male is known to patrol mainly in waters in front of the nest and swim closely to its female while feeding [20]. This resembles territorial behaviour, where the male aggressively defends the area around the female [21]. This behaviour may persist during chick-rearing and non-breeding stages, though the female is also known to defend their home range [26].

Time spent foraging

Overall, individuals living closer to settlements and to roads spent more time foraging. Such individuals are more likely to be disturbed by human activity, therefore decreasing time spent resting to compensate for foraging time loss, but also spending an increased amount of time being vigilant and moving away from humans or dogs, which could be confused with foraging behaviour in the GPS data. This explanation is supported by fieldwork observations in which Falkland Steamer Ducks, when disturbed by human activity while resting on shore, were seen swimming away and resuming foraging. The disturbance effect of recreational activity has been measured in seven different wintering duck species in the Back Bay National Wildlife Refuge, Virgina Beach, USA [33]. Unfortunately, quantifying the effects of human disturbance remains challenging, especially in a data-limited environment such as the Falkland Islands [32].

Individuals on Bleaker Island were found to spend more time foraging than those around Stanley Harbour. This was unexpected, as four individuals were living in the city itself and all but one incubating female were either nesting close to or required to cross a road to reach feeding grounds. We therefore expected a higher proportion of foraging activity among individuals in Stanley Harbour compared to those on Bleaker Island. Bleaker Island was characterised by one settlement and no concrete road. The nature of the coastline varied but human disturbance was low. On the other hand, Stanley Harbour presented a variety of human infrastructures, from occasionally visited jetties, to the city of Stanley. Disturbance therefore varied greatly depending on the specific location of each tagged individual. This highlights the slightly unreliable result from using a binary location variable as an effect in the model, as opposed to, finer-scale proxies such as distance to roads or settlements, which may offer more reliable indicators of foraging activity.

Incubating females and chick rearing individuals spent more time foraging. These individuals are likely to require more energy as they are actively involved in reproduction, and lose energy when incubating and brooding [49,50]. In our study, all females were less than 100 m away from a kelp bed (Fig 2), and this short travel distance means that they could potentially spend more time foraging before returning to their nest. On the other hand, chick-rearing parents displayed a higher frequency of foraging (Fig 6). This further supports the idea of limiting heat loss for the young ducklings while ensuring they gain the energy required for an optimal growth [53]. Time spent foraging was higher where there was more kelp cover in the wider home range but lower where there was more kelp cover within the core range.

Conclusion

This study highlighted variations in the movement ecology of the endemic Falkland Steamer Duck based on breeding status, sex, and in relation to environmental factors. Distance to human structures, used as a proxy for human disturbance, were found to affect distance travelled and time spent foraging by Falkland Steamer Ducks. Kelp beds also constrained Falkland Steamer Ducks, from the size of their home and core range to their daily activity. Daily travelled distance also increased if ducks were required to travel inland for the purposes of accessing freshwater. Breeding status constrained time spent foraging and time spent on land.

Kelp, and more specifically the dominant Macrocystis porifera¸ are engineering species which are found in dynamic coastal regions that provide nursery areas for numerous marine species such as Patagonian squid (Doryteuthis gahi), rock cod (Patagonothen spp) and the Southern blue whiting (Micromesisitius australis), and therefore provide a link with open-sea trophic webs [32,54,55]. Based on our observations and literature [18], we were expecting Falkland Steamer Duck ecology to be influenced by kelp forest as their main food source. Given that the Falkland Steamer Duck is an endemic species distributed along the entire coastline of the Falkland Islands archipelago, it holds considerable potential as an indicator species for environmental changes both terrestrial (e.g., coastal erosion, shifts in Poa flabellata [tussac] density, drying up of ponds) and marine (e.g., degradation of kelp beds). Obtaining reliable ecological information is therefore critical for accurately assessing the conservation status of the species and for developing effective management strategies to ensure its persistence—particularly in the face of climate change and its associated impacts on kelp ecosystems. The future of regional oceanographic conditions remains uncertain, with the South Atlantic Ocean experiencing warming trends while the Falkland Current appears to be cooling [32]. Such changes could have cascading ecological consequences, particularly for kelp forests, which, while historically stable [54,55], may be vulnerable to abrupt shifts. Understanding thoroughly what induces the species distribution and habitat selection throughout the entire archipelago coastline is a key step toward predicting the cascading impact of climate change on the Falkland Steamer Duck through any changes of key environmental features of the marine/terrestrial coastline interface. Continued monitoring will be essential to detect emerging ecological shifts and to inform adaptive conservation strategies in this rapidly changing region.

Supporting information

S1 Fig. Variograms for individuals with insufficient data to estimate home ranges.

Following Calabrese et al (2016) recommendation, because the curve does not reach an asymptote, the showed individuals were excluded.

(DOCX)

pone.0333302.s001.docx^{(263.3KB, docx)}

S2 Fig. Variograms for individuals with sufficient data to estimate home ranges.

Following Calabrese et al (2016) recommendation, because the curve does reach an asymptote, the showed individuals were kept.

(DOCX)

pone.0333302.s002.docx^{(384KB, docx)}

S1 Table. AIC and delta AIC for models explaining (i) travelled distance, (ii) home range, (iii) core range, (iv) proportion of time spent on land, (v) proportion time foraging.

(1/id) notation represents individual as a random effect. Bold models are single models with the best score, or multiple models used for model averaging (those within delta AIC = 4). Null models (i.e., no covariates) presented in italics.

(DOCX)

pone.0333302.s003.docx^{(20.4KB, docx)}

S3 Fig. Activity budget of the Falkland Steamer Duck.

Colours represent the different behaviours (grey: travelling; green: foraging; blue: resting) for each breeding status (CR: chick-rearing; IF: incubating female; NB: non-breeding; PM: patrolling male).

(DOCX)

pone.0333302.s004.docx^{(281.4KB, docx)}

Acknowledgments

We sincerely thank the South Atlantic Environment Research Institute for the logistic support and access to field. We also extend our gratitude to Nick Rendell and his family for their warm hospitality on Bleaker Island. We are appreciative of all the feedbacks from Dr María Laura Agüero and reviewer 1 which strengthened the structure of this publication.

Data Availability

The data are now available with the following DOI: https://doi.org/10.5281/zenodo.15309729.

Funding Statement

LL and LM’s work was partially supported by the Methusalem project (01M00221). Fieldwork was funded by the Shackleton Scholarship Fund (SSF22-019-ADC-Kristiansen and SSF23-021-ADC-Kristiansen) and the Falkland Environmental Study Budget (ESB122022). The funders had no role in the study design, data collection and analysis, decision to publish or preparation of the manuscript. There was no additional external funding received for this study.

References

1.Burt WH. Territoriality and home range concepts as applied to mammals. J Mammal. 1943;24(3):346. doi: 10.2307/1374834 [DOI] [Google Scholar]
2.Maxwell SM, Conners MG, Sisson NB, Dawson TM. Potential benefits and shortcomings of marine protected areas for small seabirds revealed using miniature tags. Frontiers in Marine Sci. 2016;3. [Google Scholar]
3.Thaxter CB, Lascelles B, Sugar K, Cook ASCP, Roos S, Bolton M, et al. Seabird foraging ranges as a preliminary tool for identifying candidate Marine Protected Areas. Biological Conservation. 2012;156:53–61. doi: 10.1016/j.biocon.2011.12.009 [DOI] [Google Scholar]
4.Donald PF, Fishpool LDC, Ajagbe A, Bennun LA, Bunting G, Burfield IJ, et al. Important Bird and Biodiversity Areas (IBAs): the development and characteristics of a global inventory of key sites for biodiversity. Bird Conservation Int. 2018;29(2):177–98. doi: 10.1017/s0959270918000102 [DOI] [Google Scholar]
5.Soanes LM, Bright JA, Angel LP, Arnould JPY, Bolton M, Berlincourt M, et al. Defining marine important bird areas: Testing the foraging radius approach. Biological Conservation. 2016;196:69–79. doi: 10.1016/j.biocon.2016.02.007 [DOI] [Google Scholar]
6.Kier G, Kreft H, Lee TM, Jetz W, Ibisch PL, Nowicki C, et al. Proceedings of the National Academy of Sciences of the United States of America. 2009;106(23):9322–7. [DOI] [PMC free article] [PubMed] [Google Scholar]
7.Tershy BR, Shen KW, Newton KM, Holmes ND, Croll DA. The importance of islands for the protection of biological and linguistic diversity. BioScience. 2015;65(6):592–7. [Google Scholar]
8.Taillie PJ, Jolly SR, Bobay LR, Sneckenberger S, McCleery RA. Habitat use across multiple scales suggests resilience to rising seas for endangered island endemic compared to sympatric invasive species. Animal Conservation. 2020;24(2):280–90. doi: 10.1111/acv.12637 [DOI] [Google Scholar]
9.Mitchell LJ, Kohler T, White PCL, Arnold KE. High interindividual variability in habitat selection and functional habitat relationships in European nightjars over a period of habitat change. Ecol Evol. 2020;10(12):5932–45. doi: 10.1002/ece3.6331 [DOI] [PMC free article] [PubMed] [Google Scholar]
10.Bengtsson D, Avril A, Gunnarsson G, Elmberg J, Söderquist P, Norevik G, et al. Movements, home-range size and habitat selection of mallards during autumn migration. PLoS One. 2014;9(6):e100764. doi: 10.1371/journal.pone.0100764 [DOI] [PMC free article] [PubMed] [Google Scholar]
11.Dahl T, Falk-Petersen S, Gabrielsen G, Sargent J, Hop H, Millar R. Lipids and stable isotopes in common eider, black-legged kittiwake and northern fulmar: a trophic study from an Arctic fjord. Mar Ecol Prog Ser. 2003;256:257–69. [Google Scholar]
12.Kilpi M, Lindström K. Habitat-specific clutch size and cost of incubation in common eiders, Somateria mollissima. Oecologia. 1997;111:297–301. [DOI] [PubMed] [Google Scholar]
13.Munday C, Rose P. Environmental and Social Influences on the Behaviour of Free-Living Mandarin Ducks in Richmond Park. Animals (Basel). 2022;12(19):2554. doi: 10.3390/ani12192554 [DOI] [PMC free article] [PubMed] [Google Scholar]
14.Agüero ML, Borboroglu PG, Esler D. Trophic Ecology of Breeding White-Headed Steamer-Duck (Tachyeres leucocephalus). Waterbirds. 2014;37(1):88–93. doi: 10.1675/063.037.0111 [DOI] [Google Scholar]
15.Weller MW. Ecological studies of Falkland Islands’ waterfowl. Wildfowl. 1972;23(23):25–44. [Google Scholar]
16.Fulton TL, Letts B, Shapiro B. Multiple losses of flight and recent speciation in steamer ducks. Proc Biol Sci. 2012;279(1737):2339–46. doi: 10.1098/rspb.2011.2599 [DOI] [PMC free article] [PubMed] [Google Scholar]
17.Livezey BC, Humphrey PS. Taxonomy and identification of steamer-ducks (Anatidae: Tachyeres). Lawrence, Kan: Museum of Natural History, University of Kansas. 1992. https://www.biodiversitylibrary.org/bibliography/8436 [Google Scholar]
18.Weller MW. Ecology and behaviour of steamer ducks. Wildfowl. 1976;27:45–53. [Google Scholar]
19.Johnsgard PA. Ducks, geese, and swans of the world, revised edition. University of Nebraska-Lincoln Libraries. 2010. [Google Scholar]
20.Agüero ML, Borboroglu PG. Breeding biology of the Chubut Steamer Duck (Tachyeres leucocephalus). Ornitological Neotropical. 2013;24:85–93. [Google Scholar]
21.Gauthier G. Territorial behaviour, forced copulations and mixed reproductive strategy in ducks. Wildfowl. 1988;39:102–14. [Google Scholar]
22.Woods RW, Woods A. Atlas of Breeding Birds of the Falkland Islands. Shropshire, England: Anthony Nelson. 1997. [Google Scholar]
23.Livezey BC, Humphrey PS. Territoriality and Interspecific Aggression in Steamer-Ducks. The Condor. 1985;87(1):154–7. [Google Scholar]
24.IUCN. Tachyeres brachypterus. The IUCN Red List of Threatened Species. https://www.iucnredlist.org/species/22680047/132524587 2018. Accessed 2025 July 17.
25.Agüero ML, Borboroglu JPG, Esler D. Nesting habitat of Chubut Steamer Ducks in Patagonia, Argentina. Emu - Austral Ornithology. 2010;110(4):302–6. [Google Scholar]
26.Cawkell EM, Hamilton JE. The birds of the falkland islands. Ibis. 1961;103A(1):1–27. doi: 10.1111/j.1474-919x.1961.tb02417.x [DOI] [Google Scholar]
27.Livezey BC. Feeding morphology, foraging behavior, and foods of steamer-ducks (Anatidae: Tachyeres). Museum of Natural History, the University of Kansas. 1989;125:1–41. [Google Scholar]
28.Nyström KGK, Pehrsson O. Salinity as a constraint affecting food and habitat choice of mussel‐feeding diving ducks. Ibis. 1988;130(1):94–110. doi: 10.1111/j.1474-919x.1988.tb00960.x [DOI] [Google Scholar]
29.Bakun A, Babcock EA, Santora C. Regulating a complex adaptive system via its wasp-waist: grappling with ecosystem-based management of the New England herring fishery. ICES Journal of Marine Science. 2009;66(8):1768–75. doi: 10.1093/icesjms/fsp073 [DOI] [Google Scholar]
30.Bakun A. Wasp-waist populations and marine ecosystem dynamics: Navigating the “predator pit” topographies. Progress in Oceanography. 2006;68(2–4):271–88. doi: 10.1016/j.pocean.2006.02.004 [DOI] [Google Scholar]
31.Van Tussenbroek BI. Plant and frond dynamics of the giant kelp,Macrocystis pyrifera, forming a fringing zone in the Falkland Islands. European Journal of Phycology. 1993;28(3):161–5. doi: 10.1080/09670269300650251 [DOI] [Google Scholar]
32.Van Der Grient J, Morley S, Arkhipkin A, Bates J, Baylis A, Brewin P. The Falkland Islands marine ecosystem: A review of the seasonal dynamics and trophic interactions across the food web. Advances in Marine Biology. Elsevier. 2023. p. S0065288123000019. [DOI] [PubMed] [Google Scholar]
33.Pease ML, Rose RK, Butler MJ. Effects of human disturbances on the behavior of wintering ducks. Wildlife Society Bulletin. 2005;33(1):103–12. doi: 10.2193/0091-7648(2005)33[103:eohdot]2.0.co;2 [DOI] [Google Scholar]
34.Upson R, Lewis R. Updated vascular plant checklist and atlas for the Falkland Islands. Falklands Conservation. 2014. [Google Scholar]
35.Poncet S. Long-term coastal monitoring of the birds of Stanley Harbour and Cape Pembroke. Island Landcare. 2023. [Google Scholar]
36.Johnsgard PA. Handbook of Waterfowl Behavior: Tribe Tachyerini (Steamer Ducks). Unknown. 1965. [Google Scholar]
37.Livezey BC, Humphrey PS. Mechanics of Steaming in Steamer-ducks. The Auk. 1983;100(2):485–8. [Google Scholar]
38.Calenge C. The package “adehabitat” for the R software: A tool for the analysis of space and habitat use by animals. Ecological Modelling. 2006;197(3–4):516–9. doi: 10.1016/j.ecolmodel.2006.03.017 [DOI] [Google Scholar]
39.Benhamou S. Dynamic approach to space and habitat use based on biased random bridges. PLoS One. 2011;6(1):e14592. doi: 10.1371/journal.pone.0014592 [DOI] [PMC free article] [PubMed] [Google Scholar]
40.Fischer JW, Walter WD, Avery ML. Brownian Bridge Movement Models to Characterize Birds’ Home Ranges. The Condor. 2013;115(2):298–305. doi: 10.1525/cond.2013.110168 [DOI] [Google Scholar]
41.Calabrese JM, Fleming CH, Gurarie E. ctmm: anrpackage for analyzing animal relocation data as a continuous‐time stochastic process. Methods Ecol Evol. 2016;7(9):1124–32. doi: 10.1111/2041-210x.12559 [DOI] [Google Scholar]
42.Horne JS, Garton EO, Krone SM, Lewis JS. Analyzing animal movements using Brownian bridges. Ecology. 2007;88(9):2354–63. [DOI] [PubMed] [Google Scholar]
43.Langrock R, King R, Matthiopoulos J, Thomas L, Fortin D, Morales JM. Flexible and practical modeling of animal telemetry data: hidden Markov models and extensions. Ecology. 2012;93(11):2336–42. doi: 10.1890/11-2241.1 [DOI] [PubMed] [Google Scholar]
44.Michelot T, Langrock R, Patterson TA. moveHMM: an R package for the statistical modelling of animal movement data using hidden Markov models. Methods Ecol Evol. 2016;7(11):1308–15. doi: 10.1111/2041-210x.12578 [DOI] [Google Scholar]
45.South A, South MA. R Package: rnaturalearth. World Map Data from Natural Earth, Version 01 0 Available online: https://cranr-projectorg/web/packages/rnaturalearth/rnaturalearth.pdf (accessed on 12 November 2024). 2017;.
46.Burnham KP, Anderson DR. Multimodel inference: understanding AIC and BIC in model selection. Sociological Methods & Research. 2004;33(2):261–304. [Google Scholar]
47.Angelstam PK, Bütler R, Lazdinis M, Roberge JM. Habitat thresholds for focal species at multiple scales and forest biodiversity conservation — dead wood as an example. 2025.
48.Kellett DK, Alisauskas RT, Mehl KR, Drake KL, Traylor JJ, Lawson SL. Body Mass of Long-Tailed Ducks (Clangula Hyemalis) During Incubation. The Auk. 2005;122(1):313–8. doi: 10.1093/auk/122.1.313 [DOI] [Google Scholar]
49.Kellett DK, Alisauskas RT. Body-mass Dynamics of King Eiders During Incubation. The Auk. 2000;117(3):812–7. doi: 10.1093/auk/117.3.812 [DOI] [Google Scholar]
50.Agüero ML, Lorenti E, Minardi G, Agu A, Berrier E, D’Amico V. Incubation pattern of endangered Chubut Steamerduck (Tachyeres leucocephalus) and environmental features: implications for conservation. In Review. 2022. [Google Scholar]
51.Humphrey PS, Livezey BC. Nest, eggs, and downy young of the white-headed flightless steamer-duck. Ornithological Monographs. 1985;36:944–53. [Google Scholar]
52.Koskimies J, Lahti L. Cold-hardiness of the newly hatched young in relation to ecology and distribution in ten species of European ducks. Auk. 1964;81(3):281–307. [Google Scholar]
53.Nye PA. Heat loss in wet ducklings and chicks. Ibis. 1964;106(2):189–97. doi: 10.1111/j.1474-919x.1964.tb03695.x [DOI] [Google Scholar]
54.Bayley D, Brickle P, Brewin P, Golding N, Pelembe T. Valuation of kelp forest ecosystem services in the Falkland Islands: A case study integrating blue carbon sequestration potential. OE. 2021;6:e62811. [Google Scholar]
55.Teagle H, Hawkins SJ, Moore PJ, Smale DA. The role of kelp species as biogenic habitat formers in coastal marine ecosystems. J Experimental Marine Biol Ecol. 2017;492:81–98. doi: 10.1016/j.jembe.2017.01.017 [DOI] [Google Scholar]

PLoS One. doi: 10.1371/journal.pone.0333302.r001

Decision Letter 0

Lee Cooper

26 Jun 2025

PONE-D-25-23682Habitat use and activity budget in the Falkland Steamer Duck (Tachyeres brachypterus)

PLOS ONE

Dear Ms. Kristiansen,

Thank you for submitting your manuscript to PLOS ONE. I have now received reviews of the paper from two experts who are knowledgeable about sea ducks, including this species, and they have made a number of constructive suggestions about how to improve the paper and communicate your Ph.D. study results. So, at this point, the paper is not suitable for acceptance, but I think the two reviewers have given you a lot to work with and I would encourage re-submission of a revised version once you have considered their recommendations.

Please submit your revised manuscript by Aug 10 2025 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org . When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols . Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols .

We look forward to receiving your revised manuscript.

Kind regards,

Lee W Cooper, Ph.D.

Section Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. Thank you for stating the following financial disclosure:

Please state what role the funders took in the study. If the funders had no role, please state: "The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript."

If this statement is not correct you must amend it as needed.

Please include this amended Role of Funder statement in your cover letter; we will change the online submission form on your behalf.

3. Thank you for stating in your Funding Statement:

Please provide an amended statement that declares *all* the funding or sources of support (whether external or internal to your organization) received during this study, as detailed online in our guide for authors at http://journals.plos.org/plosone/s/submit-now. Please also include the statement “There was no additional external funding received for this study.” in your updated Funding Statement.

Please include your amended Funding Statement within your cover letter. We will change the online submission form on your behalf.

4. Thank you for stating the following in the Acknowledgments Section of your manuscript:

LL and LM’s work was partially supported by the Methusalem project (01M00221). Fieldwork

was funded by the Shackleton Scholarship Fund (SSF22-019-ADC-Kristiansen and SSF23-

021-ADC-Kristiansen) and the Falkland Environmental Study Budget (ESB122022). We

sincerely thank the South Atlantic Environment Research Institute for the logistic support and

access to field. We also extend our gratitude to Nick Rendell and his family for their warm

hospitality on Bleaker Island.

We note that you have provided funding information that is not currently declared in your Funding Statement. However, funding information should not appear in the Acknowledgments section or other areas of your manuscript. We will only publish funding information present in the Funding Statement section of the online submission form.

Please remove any funding-related text from the manuscript and let us know how you would like to update your Funding Statement. Currently, your Funding Statement reads as follows:

Please include your amended statements within your cover letter; we will change the online submission form on your behalf.

5. Thank you for stating the following in the Competing Interests section:

No.

Please confirm that this does not alter your adherence to all PLOS ONE policies on sharing data and materials, by including the following statement: "This does not alter our adherence to PLOS ONE policies on sharing data and materials.” (as detailed online in our guide for authors http://journals.plos.org/plosone/s/competing-interests). If there are restrictions on sharing of data and/or materials, please state these. Please note that we cannot proceed with consideration of your article until this information has been declared.

Please include your updated Competing Interests statement in your cover letter; we will change the online submission form on your behalf.

6. When completing the data availability statement of the submission form, you indicated that you will make your data available on acceptance. We strongly recommend all authors decide on a data sharing plan before acceptance, as the process can be lengthy and hold up publication timelines. Please note that, though access restrictions are acceptable now, your entire data will need to be made freely accessible if your manuscript is accepted for publication. This policy applies to all data except where public deposition would breach compliance with the protocol approved by your research ethics board. If you are unable to adhere to our open data policy, please kindly revise your statement to explain your reasoning and we will seek the editor's input on an exemption. Please be assured that, once you have provided your new statement, the assessment of your exemption will not hold up the peer review process.

7. Please amend the manuscript submission data (via Edit Submission) to include author Sébastien Dupray.

8. Please amend your authorship list in your manuscript file to include author Sébastien A.P. Dupray

9. Please ensure that you refer to Figure 3 in your text as, if accepted, production will need this reference to link the reader to the figure.

10. Please include a caption for figure 5.

11. We note that Figures 1 and 2 in your submission contain map images which may be copyrighted. All PLOS content is published under the Creative Commons Attribution License (CC BY 4.0), which means that the manuscript, images, and Supporting Information files will be freely available online, and any third party is permitted to access, download, copy, distribute, and use these materials in any way, even commercially, with proper attribution. For these reasons, we cannot publish previously copyrighted maps or satellite images created using proprietary data, such as Google software (Google Maps, Street View, and Earth). For more information, see our copyright guidelines: http://journals.plos.org/plosone/s/licenses-and-copyright.

We require you to either (a) present written permission from the copyright holder to publish these figures specifically under the CC BY 4.0 license, or (b) remove the figures from your submission:

a. You may seek permission from the original copyright holder of Figures 1 and 2 to publish the content specifically under the CC BY 4.0 license.

We recommend that you contact the original copyright holder with the Content Permission Form (http://journals.plos.org/plosone/s/file?id=7c09/content-permission-form.pdf) and the following text:

“I request permission for the open-access journal PLOS ONE to publish XXX under the Creative Commons Attribution License (CCAL) CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). Please be aware that this license allows unrestricted use and distribution, even commercially, by third parties. Please reply and provide explicit written permission to publish XXX under a CC BY license and complete the attached form.”

Please upload the completed Content Permission Form or other proof of granted permissions as an ""Other"" file with your submission.

In the figure caption of the copyrighted figure, please include the following text: “Reprinted from [ref] under a CC BY license, with permission from [name of publisher], original copyright [original copyright year].”

b. If you are unable to obtain permission from the original copyright holder to publish these figures under the CC BY 4.0 license or if the copyright holder’s requirements are incompatible with the CC BY 4.0 license, please either i) remove the figure or ii) supply a replacement figure that complies with the CC BY 4.0 license. Please check copyright information on all replacement figures and update the figure caption with source information. If applicable, please specify in the figure caption text when a figure is similar but not identical to the original image and is therefore for illustrative purposes only.

The following resources for replacing copyrighted map figures may be helpful:

USGS National Map Viewer (public domain): http://viewer.nationalmap.gov/viewer/

The Gateway to Astronaut Photography of Earth (public domain): http://eol.jsc.nasa.gov/sseop/clickmap/

Maps at the CIA (public domain): https://www.cia.gov/library/publications/the-world-factbook/index.html and https://www.cia.gov/library/publications/cia-maps-publications/index.html

NASA Earth Observatory (public domain): http://earthobservatory.nasa.gov/

Landsat: http://landsat.visibleearth.nasa.gov/

USGS EROS (Earth Resources Observatory and Science (EROS) Center) (public domain): http://eros.usgs.gov/#

Natural Earth (public domain): http://www.naturalearthdata.com/

12. Please include a copy of Table 3 which you refer to in your text on page 7.

13. Please include captions for your Supporting Information files at the end of your manuscript, and update any in-text citations to match accordingly. Please see our Supporting Information guidelines for more information: http://journals.plos.org/plosone/s/supporting-information.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: No

Reviewer #2: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: This paper provides new descriptive information on an interesting and little-studied species. The paper would be improved if a better context were provided to motivate collection of the descriptive data. The study is justified as collection of baseline information, but the usefulness of data on home range sizes and activity budgets depends on the types of change anticipated and how the data could be applied to problems that might arise. Distance to kelp and distance to human structures were logical candidates for possible change. However, finding that the birds traveled farther when distance to kelp was greater does not imply constraint when the areal extent of kelp in the home range had no effect, and distance to human structures does not seem a problem because the birds fed more the closer they were to structures. The overall conclusion that climate-driven changes in kelp availability are expected to negatively affect the species is not derived from or justified by analyses presented in this paper, which showed that kelp availability had little effect on movements or home range size.

The manuscript could also be more carefully prepared, as noted in the comments below. I have made a number of suggestions that might help improve the paper.

1. L 10. Replace “conversation” with “conservation”

2. L 19-20. Insert “birds of different” before “breeding status”

3. L 21-23. This conclusion is not logical or compelling as stated. The sentence first states that kelp beds occur “all over the archipelago” and are thus perhaps far from limiting in availability, but then warns that any changes in density of kelp beds are “expected to negatively impact the species”. To draw such a conclusion, some quantification of the area of this habitat available vs. the area of this habitat occupied by the current steamer duck population is needed.

Moreover, what do you mean by kelp “density”? Fraction of total area occupied by kelp habitats? Biomass of kelp per unit area of habitat? This qualitative conjecture could have been stated anecdotally without conducting the study, so please back it up with specific analyses.

4. In general, the Abstract should contain more specific results. What were the distances traveled and home and core range sizes among birds of different pair status (or at least the ranges observed). What were percentages of time spent in different behaviors? What specific variables led you to your final statement that changes in the density of kelp beds would negatively the species? I suggest substantially reducing the first half of the Abstract which is all introductory, and then providing some specific, quantitative findings. The Abstract is important for people who will not read the paper, so you need to provide more substance.

5. L 32-33. The passage should read “… invasive species, climate change, and inaccessibility often …”

6. L 34-40. This paragraph adds little that ecologists reading the paper do not already know. I suggest deleting the paragraph.

7. L 41-44. The first sentence of this paragraph can be deleted with no loss of information important to this paper. Eliminate summaries of general knowledge and get to the substance of specific questions you will address in this study.

8. L 47. Explain what you mean by “passive defence”

9. L 49-50. To be more concise, I suggest ‘Territories of marine waterfowl encompass both marine and terrestrial habitats.”

10. L 53. I strongly suggest that you avoid acronyms unless the terms are really ponderous. Busy scientists often do not have time to read a paper in one sitting within the same few days, and may skip around in a paper to find particular information. Consequently, it is quite annoying have to search back through a paper to find what a particular acronym stands for.

11. L 57. Replace “apparent” by “apparently”. The pairbonds are not apparent, they are apparently long-term.

12. L 60. Replace “animal” by “bird and mammal” if that’s what you mean. I suspect there are endemic insects, arachnids, or other invertebrates that you have not considered in this general statement about animals.

13. L 63. I suggest deleting “interfacing” as unnecessary, and replacing “comprise” by “include”

14. L 69. Do you mean “these factors”, referring to sex, breeding status, and location mentioned in the preceding sentence? Why would you expect these factors to result in differences in these activities? You have not commented on potential reasons in preceding text, but such expectations could provide you with more specific predictions (and related conclusions) based on ecological processes of interest to a general readership.

15. L 83-84. How far inland do the ducks nest?

16. L 117. Please state clearly whether “daily distance traveled” was along the trajectory of movement rather than the maximum linear distance moved between the beginning and end of the day.

17. L 118-119. For the many readers who will not know, please explain briefly what the “random bridge kernel method” does.

18. L 120. What does “UD” stand for? An intuitive variable name is desirable.

19. L 123. Again, please explain in one or two sentences how “Hidden Markov Models” work.

20. L 124. Delete “in each of three ecologically relevant states (i.e.”. Based on GPS readings every 2 min, please explain how you discriminated resting vs. foraging in one place, and moving among nearby foraging patches vs. commuting.

21. L 148. Two days seems inadequate for defining an individual’s home range. Did you examine the data to see after how many days the home ranges mostly stabilized? Some standards for adequate sample size (in days) seem important to unbiased estimates of true home range size.

22. Figure 2. Panels A, B, D, and E are nice depictions of the ducks’ movements. However, the green areas that supposedly show foraging areas in panels C and F are effectively impossible to see, even when scrutinized with a magnifying glass. A reader with red-green color blindness would have no chance of discriminating what is shown in this figure. I suggest that panels C and F be moved into a separate figure, enlarged, and alternative colors selects (perhaps yellow for foraging).

What is represented by the areas in beige?

23. Table 1. Please state clearly in the caption whether the distances traveled were al What ong the trajectory of movement or were the linear distance between points at the start and end of the day. Please also specify “km/day” (not just km) as the units in the table heading. How did you standardize the core and home range sizes among individuals that were tracked for a little as 2 days to as much as 43 days (see L 148). Ranges of the birds are likely to differ substantially between such short and long tracking periods. Without better explanation of how you standardized and calculated these values, it’s not clear that results for different groups can be directly compared.

24. Tables 1 and 2 are both labeled as Table 1. “Dependent” is misspelled in what should be Table 2.

25. Table 2. Here and elsewhere in the paper, I suggest replacing “location” with “study site” to clarify what you mean (if in fact that’s what you mean). In this paper, you have locations every 2 min via the GPS, but two different study sites.

I also suggest “dist to kelp” and “dist to structure”, which are not much longer and clarify what the variable represents.

26. Table 2. The second and third variables for Distance per day are exactly the same, yet you assign them different values of AIC and ΔAIC.

27. Table 2. “hour.FI” (under Proportion of time on land) has not been defined as a variable, and I cannot guess what it might be.

28. What should be Table 3 is labeled as Table 2. Please designate the units for Distance traveled as km/day (not just km), and spell out the variable “Int”.

29. P 17. The authors stopped numbering lines at the beginning of P 17, and in fact do not include page numbers for any pages in the manuscript. These omissions make it harder to reference particular lines of text.

30. P 17, par 2, L 2. Please be specific in use of the term “home range” and “territory”, as they have different meanings. A home range is simply an area occupied, whereas a territory is actively defended. If in this sentence you mean that the non-breeding pairs defended these areas, replace “held” by “defended”. If they were occupying these areas without defense, then replace “held” by “occupied”.

31. P 17, par 4, L 1. Figure 4 (cited at the end of this sentence) shows only effects of breeding status, so delete “time of day and” from L 1. Time of day is dealt with in the last sentence of the paragraph.

32. The captions for Figures 3 and 4 at the bottom of P 17 are correctly numbered, but the figures cited as 4 and 5 in the preceding paragraph should be cited as 3 and 4, given that the original Fig. 3 included with the paper is never cited or mentioned in the manuscript.

33. P 18, par 3. I suggest that you do not attribute importance to differences that you found not to be significant, without citing actual P-values or effect sizes.

34. P 19, L 3. Delete “breeding”, or else use “sex of breeding birds” if that’s what you mean.

35. P 20, par 2, L 6. Please briefly explain the concept of “dear enemy”, which will be unfamiliar to many readers.

36. P 20, par 2, L 9. Replace “mean in” with “means by”

37. P 21, par 3, L 6. Insert “by” before “kelp forest”

38. P 21, par 3, L 9. “patting”? I have never seen this term applied to birds, so please define or substitute a more widely recognized term.

39. P 21, last 2 lines. You have presented no evidence that kelp is limiting to these ducks, and in fact your data indicate that sizes of their home ranges or defended areas are unaffected by the local availability of kelp. You have presented no evidence that these ducks forage preferentially in kelp beds. Perhaps you can cite other studies that have data to show such relationships, but you have not mentioned them.

40. The Discussion section on Time spent foraging and the Conclusion contain a fair amount of speculation about factors not really addressed in this paper. I suggest sticking to arguments for which you present more relevant data.

Reviewer #2: General Comments

This manuscript, "Habitat use and activity budget in the Falkland Steamer Duck (Tachyeres brachypterus)," presents novel findings for this endemic sea duck species in the Falkland Islands, addressing significant information gaps.

I believe its publication is highly important, as it provides systematic and rigorous data that can be valuable for zoning and management plans in the area. However, the authors need to organize the information more effectively to enhance readability and understanding. They propose analyses that are not clearly specified in the aims, the results section lacks full organization, and at least two figures are illegible.

Given the emphasis on the importance of kelp beds for the species (which I agree with), this topic should be more thoroughly introduced. I recommend adding references related to the FSD's diet. Specifically, I suggest reviewing Livezey (1989), "Feeding morphology, foraging behavior and food of Steamer-ducks (Anatidae: Tachyeres)," Occasional Papers of the Museum of Natural History, University of Kansas.

Introduction

(Line 54-55) “…..found solely in South America and the FLK (25,26)”

Suggestion: I suggest changing this to "southern South America," as the Falkland Islands are included within the continental shelf.

(Line 62) You could mention that the IUCN categorized this species as "Least Concern" based on a lack of detailed information, highlighting the importance of the current study.

(Line 61) “Such information is crucial as their marine-terrestrial interfacing territories comprise, amongst other features, kelp (mainly Macrocystis pyrifera (32)) and inland vegetation assemblages (33) which may be impacted by the predicted climate change increase of 1.8 °C before the end of the century (34).”

Suggestion: You might introduce some preliminary information about the feeding methods and diet of FSDs (Livezey 1989) here. This would help establish a clearer link to your hypothesis regarding the stronger presence of kelp beds within the species' core home range.

Methods

(Line 75) As you have described the characteristics of the coastline in Bleaker Island, I believe you must do the same for Stanley Harbour. This is especially relevant in light of Livezey (1989), where the author states that "...SD on both fresh and salt water were observed more frequently along shores dominated by rock outcrops and stony beaches, and less frequently on sandy or muddy shorelines..."

(Line 92) Breeding status categories:

How did you determine males were partners of incubating females? Were males patrolling the shoreline in front of nests where females were incubating?

Similarly, how did you determine the "non-breeding" category? Were these individuals grouped far from breeding pairs (a characteristic behavior of juvenile steamer ducks)?

How did you determine the sex of non-breeding individuals, especially given that non-breeding juveniles often have confusing plumage?

Suggestion: Perhaps a more appropriate categorization would be "Adults" (including incubating females and patrolling males) and "Juveniles."

(Line 101) How long did the GPS data logger track individuals (e.g., 1 month? 1 year?)? Instead of only specifying that data collection lasted until the logger was shed or the battery failed, you should specify the range/average time during which you tracked individuals.

(Line 104) I believe you must aggregate "...determine environmental factors that affect FSD behavior" within your aims section. Additionally, you should clearly specify the behavioral categories you had in mind for evaluating habitat use, activity budget, and the effects of environmental variables.

(Line 106-107) As mentioned previously, you need to introduce available information about the importance of kelp beds as feeding habitat for FSDs. You could cite Livezey (1989) here.

(Line 111-112) Perhaps a more appropriate variable would be the area of the kelp bed polygon, serving as a proxy for the amount of available food, given that kelp beds harbor a great diversity of steamer duck food items.

(Line 124) "Resting, foraging, commuting" are three categories of behavior, not ecologically relevant states.

(Line 126) Please specify this as an aim.

Several analyses you mentioned are not specified in the aims section. I think it is important to list them: "...factors influencing (1) FSD behavior, (2) daily distances traveled (km), (3) the size of the core and wider home ranges, (4) variation in the proportion of time spent foraging per hour of the day, and (5) time spent on land."

Do you consider time spent on land as resting behavior?

Pay close attention to the use of "home range" and "habitat use" terms.

"Home range refers to the spatial area that an animal or group of animals regularly uses to conduct all its normal vital activities. This includes foraging, reproduction, offspring care, resting, etc."

However, "habitat use refers to what kind of resources and features, present within its home range or within a broader area (e.g., the landscape), an animal or population utilizes to cover their needs. It's not just about where the animal moves, but what specific 'elements' of that place are used."

Your methods allowed you to determine home and core range, but not habitat use. To determine habitat use, you would need to sample the resources that FSDs use. For example, to determine breeding habitat use, you could focus on environmental features individuals use for nesting (microhabitat scale), such as vegetation, nest material, distance to the coastline, soil, etc.

Results

(Line 149-153) The "breeding status category" and the "amount of individuals of each sex within these categories" are not entirely clear until this paragraph. I think you should move this information to the methods section and clarify if the "non-breeding" category corresponds to juveniles or adults suspected of breeding season failure.

(Page 17) When you mention, “The hour of day was also significant (P < 0.01). Proportion of time spent on peaked above 0.50 at 4:00 and 11:00, then reached a minimum of 0.32 at 22:00,” are you referring to incubating females?

Does it have any biological sense to test the effect of the "incubating females" category on "time spent on land"? Perhaps I am misunderstanding the meaning of "time spent on land." Could it encompass resting, incubation, or patrolling? Does "on land" refer to the coastline, inland areas, or both?

Discussion

According to Table 2, breeding status (IF) and location were significant for travelled distance, and only sex (M) was significant for core range. The first paragraph of this section is unclear.

“In particular, we reveal that kelp distribution and distance to settlements influences FSD ecology, and more precisely its daily travelling distances and time spent foraging.”

“Home range sizes were larger at Stanley Harbour than Bleaker Island though not significantly. This may reflect birds needing to travel further to find suitable habitat.”

Why do you think this? Do you have any references to cite that support this explanation?

“Non-breeding pairs had the greatest variation between their home and core ranges, which could be linked to territorial behaviours such as patrolling and defence against intruders (31,48).”

What could be the possible explanation for the differences in home and core range between non-breeding individuals (assuming they are not juveniles) and "patrolling males"? That is, territorial behavior and aggressive defense are common during the breeding season. Therefore, this explanation does not sound like a suitable explanation for your results in this context.

“Core range was larger for males than females. This could originate from different behaviours. During incubation, the male is known to patrol mainly in waters in front of the nest and swim closely to its female while feeding (29). This resembles a form of territorial behaviour, where the male aggressively…”

Considering that your work was conducted during the breeding season, and adding that males patrol the marine coastal section in front of incubating females (Agüero and García Borboroglu 2013), "patrolling males" and "incubating females" could be considered as a "breeding pair" unit. In this case, home and core range could be obtained by the overlap between "patrolling males" and "their incubating females."

Home and core range are the places where all biologically important activities occur (feeding, breeding, resting, etc.). The fact that females spend more time on land and use this habitat while their male is patrolling the water territory has to do with the fact that only females incubate eggs. However, this does not mean that land used for nesting and water territory should be considered as different core ranges between sexes. I think the best way to test home range differences between sexes would be to track individuals outside the breeding season, or perhaps more appropriately, between age classes (pairs and juveniles), taking into account that steamer ducks are paired year-round and juveniles often group far from pairs.

(Page 21) “...For example, integrating the distance from kelp beds to the shoreline, and when possible, to nesting sites, may offer a more refined understanding of habitat use….”

Do you have the geolocations of kelp beds and nests of the incubating females you tracked? If so, you might consider adding this analysis to improve your manuscript, especially given that many of your potential explanations refer to the importance of kelp beds for FSDs.

(Page 22) “This study represents the first investigation into the movement ecology of FSD using high resolution GPS tracking. Our results demonstrate that breeding status, sex, geographic location, and kelp distribution all significantly influence different facets of its movement ecology. Our findings establish a baseline for understanding the spatial ecology of FSD and highlight the species’ potential role as a sentinel of environmental change.”

Suggestion: I agree; this paragraph would be a great sentence to head the Discussion section.

I could not understand the figures because they are in low resolution, so unreadable. Please improve them.

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean? ). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy .

Reviewer #1: No

Reviewer #2: Yes: MARIA LAURA AGüERO

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/ . PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org . Please note that Supporting Information files do not need this step.

PLoS One. 2025 Oct 7;20(10):e0333302. doi: 10.1371/journal.pone.0333302.r002

Author response to Decision Letter 1

4 Sep 2025

Reviewer #1:

This paper provides new descriptive information on an interesting and little-studied species. The paper would be improved if a better context were provided to motivate collection of the descriptive data. The study is justified as collection of baseline information, but the usefulness of data on home range sizes and activity budgets depends on the types of change anticipated and how the data could be applied to problems that might arise. Distance to kelp and distance to human structures were logical candidates for possible change. However, finding that the birds traveled farther when distance to kelp was greater does not imply constraint when the areal extent of kelp in the home range had no effect, and distance to human structures does not seem a problem because the birds fed more the closer they were to structures. The overall conclusion that climate-driven changes in kelp availability are expected to negatively affect the species is not derived from or justified by analyses presented in this paper, which showed that kelp availability had little effect on movements or home range size.

The manuscript could also be more carefully prepared, as noted in the comments below. I have made a number of suggestions that might help improve the paper.

We thank you for your feedback, your thorough read through and multiple suggestions. We certainly take into account the way that the information has been presented, and that we could have clarified elements better in order to present our arguments. We hope that the addition of the absolute kelp area helps to clarify the relationship between kelp beds and the species and that the manuscript now flows better and present stronger results.

1. L 10. Replace “conversation” with “conservation”

This has been changed. The sentence now reads as follows:

“The Falkland Islands support globally important populations of seabirds and coastal birds, underscoring their value for international conservation efforts.” (lines 9-10).

2. L 19-20. Insert “birds of different” before “breeding status”

The sentence was removed as the abstract was updated after the analysis was run again.

Thank you for this feedback, we agree with your point that we did not adequately test the relationship with kelp. Now, we have included both absolute area of kelp (in m2) and proportion of kelp within both the 50% and 95% ranges of each individual. We found that an increase in absolute kelp area leads to an increase in home range size and decrease in core range size. We also found that time spent foraging increased in the home range when the absolute area of kelp increased. The opposite pattern was found for core (50%) range. We thus hypothesise that the steamer ducks will have to adjust their home and core range sizes and change their activity budget, according to the amount of kelp area and distance to kelp. To maintain the same time spent foraging, they would rest less to compensate for the increased distance they would have to travel. The sentence now reads as follows:

“ Kelp beds are present in coastal waters all over the archipelago and, consequently, likely influence the distribution and density of Steamer ducks. Therefore, any changes in their absolute area are expected to negatively impact the species.” (lines 20-23).

Thank you for your suggestions. We reduced the introductory part, provided the main outputs from the different models, and we hope the updated version aligns more with what you were expecting to find in an abstract.

5. L 32-33. The passage should read “… invasive species, climate change, and inaccessibility often …”

Thank you for the correction. We edited as suggested. The sentence now reads as follows:

“Additional constraints to endemic species success, such as competition with invasive species and climate change (6,7) often result in data limitations hindering their conservation.

6. L 34-40. This paragraph adds little that ecologists reading the paper do not already know. I suggest deleting the paragraph.

Thank you for the suggestion. This paragraph was indeed deleted to allow more room for additional information on the coastal habitats.

Thank you for the suggestion. This sentence was indeed deleted.

8. L 47. Explain what you mean by “passive defence”

Thank you for the comment. We added two behaviours the steamer ducks use as passive defence which are patrolling and calling. The sentence was removed as a consequence of reshaping the introduction, however.

9. L 49-50. To be more concise, I suggest ‘Territories of marine waterfowl encompass both marine and terrestrial habitats.”

Thank you for the suggestion. The sentence was indeed replaced as is (lines 39-40).

11. L 57. Replace “apparent” by “apparently”. The pairbonds are not apparent, they are apparently long-term.

Thank you for the correction. The sentence now reads as follows:

“Individuals of this genus form apparently long-term pair-bonds (3), guarding well-defended territories year-round (6), with incubation conducted solely by females (7) and the territory revolving around her (8).” (lines 48-50).

Thank you for the suggestion. The sentence now reads as follows:

“The Falkland Steamer Duck, one of only two endemic bird and mammal species on the Falkland Islands, along with Cobb’s wren (Troglodytes cobbi, is ubiquitous along the coastlines.” (lines 50-52).

13. L 63. I suggest deleting “interfacing” as unnecessary, and replacing “comprise” by “include”

Thank you for the suggestion. The introduction was partly reshaped to describe better the importance of both the inland and at sea habitat, so this has been removed.

Thank you for your feedback. We have moved this section, and expanded on it to clarify, to the paragraph detailing the aims (lines 71-85).

15. L 83-84. How far inland do the ducks nest?

Thank you for this question. We have only one reference to this question, which has been added in as follows:

“On the Falkland Islands, on the south bank of Stanley Harbour, one pair of Falkland Steamer Ducks had a nest around 0.8km away from the shore, on the north side of the harbour (26), comprising a high proportion of shrub vegetation and ferns.” (lines 58-61).

16. L 117. Please state clearly whether “daily distance traveled” was along the trajectory of movement rather than the maximum linear distance moved between the beginning and end of the day.

Thank you for your comment. The sentence now reads as follows:

“Movement tracks were then interpolated at 2 min intervals using the adehabitatLT package (36) and daily distances travelled (km) were calculated along the trajectory of movement.” (lines 130-132).

17. L 118-119. For the many readers who will not know, please explain briefly what the “random bridge kernel method” does.

Thank you for your suggestion. The following sentences should explain better what the biased-random-bridge kernel method does:

“We defined home range based on two levels of the Utilisation Distribution (UD) obtained via the biased-random bridge kernel method (39). This method produces an occurrence distribution, rather than a true extrapolated home range, and represents a version of Brownian bridges (42) using the movement-based kernel density estimation. We estimated the wider home range (UD95) and core range (UD50), representing the area in which the individual can be found 95 % and 50 % of the tracked time.” (lines 138-143).

18. L 120. What does “UD” stand for? An intuitive variable name is desirable.

Thank you for the correction. UD is frequently abbreviated as such but is now better described in the previously mentioned paragraph:

“. We estimated the wider home range (UD95) and core range (UD50), representing the area in which the individual can be found 95 % and 50 % of the tracked time.” (lines 141-143).

19. L 123. Again, please explain in one or two sentences how “Hidden Markov Models” work.

Thak you for the comment. The following sentences were added:

“From the GPS locations of each individual, three ecologically relevant statuses (resting, foraging and travelling) were determined using Hidden Markov Models. These models rely on an observable set of data (here the tracking data for each individual), to infer a non-observable state dependent on the distance and angle between subsequent points (step length, and turning angle) (43). Using the moveHMM package (44), we defined the form of each state, which were then used to estimate the proportion (%) of time spent in each states.” (lines 155-163).

Thank you for the comment. The suggested phrase was indeed deleted, and the following sentences were added instead:

“Resting is depicted as having the lowest step length and low turning angles. Commuting is best described by rapid movements, that is to say long step length and low turning angles. Whereas sharp turning angles and lower step lengths indicating more tortuous movements, indicative of exploration, represent foraging” (lines 160-163).

Thank you for pointing this issue out, we agree that confirmation is necessary to know which individuals to use. We found that even with two days of data for some individuals we were able to calculate a stable home range. We did however remove some individuals from the analysis after conducting preliminary exploration.

We used the variograms from the workflow described by Calabrese et al 2016. Any individual where semi-variance was reached and remained as an asymptote were kept for the home and core range analysis. The following sentences were added:

“Firstly, to identify resident individuals for whom we had sufficient data to calculate the home range, we produced variograms using the ‘variogram’ function from the ctmm package. Individuals were considered resident when the variograms approached an asymptote (39). Any individuals that did not reach or maintain an asymptote were not considered for home and core range analysis.” (lines 134-138).

What is represented by the areas in beige?

Thank you and apologies for the for the oversight. The beige represents kelp beds. Figure 2 and its caption were changed accordingly. The caption now reads as follows:

“Fig. 2 Movement tracks of birds tagged on Stanley (A) and Bleaker Island (C), with their associated home and core ranges (respectively B and D). Home and core ranges with sufficient data were coloured in black (males) and red (females) while nominal home and core ranges with insufficient data were coloured in light grey (males) and orange (females). Kelp beds were represented in beige.” (lines 193-196).

23. Table 1. Please state clearly in the caption whether the distances traveled were along the trajectory of movement or were the linear distance between points at the start and end of the day. Please also specify “km/day” (not just km) as the units in the table heading. How did you standardize the core and home range sizes among individuals that were tracked for a little as 2 days to as much as 43 days (see L 148). Ranges of the birds are likely to differ substantially between such short and long tracking periods. Without better explanation of how you standardized and calculated these values, it’s not clear that results for different groups can be directly compared.

Thank you for your detailed feedback. The table was changed accordingly (line 203).

As now mentioned in the methods, only individuals with enough data were kept (see comment 21). This implies that enough data were collected to map reliably the home and core ranges. Additionally, models were weighted with track duration when needed:

“For all models, track duration was added as a weight when relevant and fit was assessed by simulating residuals in the DHARMa package.” (lines 169-170).

24. Tables 1 and 2 are both labeled as Table 1. “Dependent” is misspelled in what should be Table 2.

Thank you for highlighting those issues. They have been corrected according, and table 2 now sits in the supplementary information so as not to disrupt the flow of the paper (line 195 and S3 Table).

I also suggest “dist to kelp” and “dist to structure”, which are not much longer and clarify what the variable represents.

Thank you for these suggestions. Table 2 was changed accordingly and “location” replaced by “study site” throughout the manuscript.

26. Table 2. The second and third variables for Distance per day are exactly the same, yet you assign them different values of AIC and ΔAIC.

Attachment

Submitted filename: Response to Reviewers.docx

pone.0333302.s006.docx^{(54.1KB, docx)}

PLoS One. doi: 10.1371/journal.pone.0333302.r003

Decision Letter 1

Lee Cooper

11 Sep 2025

Home range and activity budget in the Falkland Steamer Duck (Tachyeres brachypterus)

PONE-D-25-23682R1

Dear Alix,

I have reviewed the significant changes you have made to the prior version of the manuscript in response to the two reviews and I am pleased to inform you that I judge that your manuscript has been revised satisfactorily and is suitable for publication. It will be formally accepted for publication once it meets any outstanding technical requirements identified by the Editorial Office. Thank you for considering PLOS ONE and for preparing this contribution that improves knowledge of this understudied waterfowl species.

The sequence of events to follow, leading to the publication of your paper are as follows:

Within one week, you’ll receive an e-mail detailing any required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice will be generated when your article is formally accepted. Please note, if your institution has a publishing partnership with PLOS and your article meets the relevant criteria, all or part of your publication costs will be covered. Please make sure your user information is up-to-date by logging into Editorial Manager at Editorial Manager® and clicking the ‘Update My Information' link at the top of the page. For questions related to billing, please contact billing support .

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Lee W Cooper, Ph.D.

Section Editor

PLOS ONE

PLoS One. doi: 10.1371/journal.pone.0333302.r004

Acceptance letter

Lee Cooper

PONE-D-25-23682R1

PLOS ONE

Dear Dr. Kristiansen,

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now being handed over to our production team.

At this stage, our production department will prepare your paper for publication. This includes ensuring the following:

* All references, tables, and figures are properly cited

* All relevant supporting information is included in the manuscript submission,

* There are no issues that prevent the paper from being properly typeset

You will receive further instructions from the production team, including instructions on how to review your proof when it is ready. Please keep in mind that we are working through a large volume of accepted articles, so please give us a few days to review your paper and let you know the next and final steps.

Lastly, if your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

You will receive an invoice from PLOS for your publication fee after your manuscript has reached the completed accept phase. If you receive an email requesting payment before acceptance or for any other service, this may be a phishing scheme. Learn how to identify phishing emails and protect your accounts at https://explore.plos.org/phishing.

If we can help with anything else, please email us at customercare@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Lee W Cooper

Section Editor

PLOS ONE

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

S1 Fig. Variograms for individuals with insufficient data to estimate home ranges.

Following Calabrese et al (2016) recommendation, because the curve does not reach an asymptote, the showed individuals were excluded.

(DOCX)

pone.0333302.s001.docx^{(263.3KB, docx)}

S2 Fig. Variograms for individuals with sufficient data to estimate home ranges.

Following Calabrese et al (2016) recommendation, because the curve does reach an asymptote, the showed individuals were kept.

(DOCX)

pone.0333302.s002.docx^{(384KB, docx)}

S1 Table. AIC and delta AIC for models explaining (i) travelled distance, (ii) home range, (iii) core range, (iv) proportion of time spent on land, (v) proportion time foraging.

(DOCX)

pone.0333302.s003.docx^{(20.4KB, docx)}

S3 Fig. Activity budget of the Falkland Steamer Duck.

(DOCX)

pone.0333302.s004.docx^{(281.4KB, docx)}

Attachment

Submitted filename: Response to Reviewers.docx

pone.0333302.s006.docx^{(54.1KB, docx)}

Data Availability Statement

The data are now available with the following DOI: https://doi.org/10.5281/zenodo.15309729.

[pone.0333302.ref001] 1.Burt WH. Territoriality and home range concepts as applied to mammals. J Mammal. 1943;24(3):346. doi: 10.2307/1374834 [DOI] [Google Scholar]

[pone.0333302.ref002] 2.Maxwell SM, Conners MG, Sisson NB, Dawson TM. Potential benefits and shortcomings of marine protected areas for small seabirds revealed using miniature tags. Frontiers in Marine Sci. 2016;3. [Google Scholar]

[pone.0333302.ref003] 3.Thaxter CB, Lascelles B, Sugar K, Cook ASCP, Roos S, Bolton M, et al. Seabird foraging ranges as a preliminary tool for identifying candidate Marine Protected Areas. Biological Conservation. 2012;156:53–61. doi: 10.1016/j.biocon.2011.12.009 [DOI] [Google Scholar]

[pone.0333302.ref004] 4.Donald PF, Fishpool LDC, Ajagbe A, Bennun LA, Bunting G, Burfield IJ, et al. Important Bird and Biodiversity Areas (IBAs): the development and characteristics of a global inventory of key sites for biodiversity. Bird Conservation Int. 2018;29(2):177–98. doi: 10.1017/s0959270918000102 [DOI] [Google Scholar]

[pone.0333302.ref005] 5.Soanes LM, Bright JA, Angel LP, Arnould JPY, Bolton M, Berlincourt M, et al. Defining marine important bird areas: Testing the foraging radius approach. Biological Conservation. 2016;196:69–79. doi: 10.1016/j.biocon.2016.02.007 [DOI] [Google Scholar]

[pone.0333302.ref006] 6.Kier G, Kreft H, Lee TM, Jetz W, Ibisch PL, Nowicki C, et al. Proceedings of the National Academy of Sciences of the United States of America. 2009;106(23):9322–7. [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0333302.ref007] 7.Tershy BR, Shen KW, Newton KM, Holmes ND, Croll DA. The importance of islands for the protection of biological and linguistic diversity. BioScience. 2015;65(6):592–7. [Google Scholar]

[pone.0333302.ref008] 8.Taillie PJ, Jolly SR, Bobay LR, Sneckenberger S, McCleery RA. Habitat use across multiple scales suggests resilience to rising seas for endangered island endemic compared to sympatric invasive species. Animal Conservation. 2020;24(2):280–90. doi: 10.1111/acv.12637 [DOI] [Google Scholar]

[pone.0333302.ref009] 9.Mitchell LJ, Kohler T, White PCL, Arnold KE. High interindividual variability in habitat selection and functional habitat relationships in European nightjars over a period of habitat change. Ecol Evol. 2020;10(12):5932–45. doi: 10.1002/ece3.6331 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0333302.ref010] 10.Bengtsson D, Avril A, Gunnarsson G, Elmberg J, Söderquist P, Norevik G, et al. Movements, home-range size and habitat selection of mallards during autumn migration. PLoS One. 2014;9(6):e100764. doi: 10.1371/journal.pone.0100764 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0333302.ref011] 11.Dahl T, Falk-Petersen S, Gabrielsen G, Sargent J, Hop H, Millar R. Lipids and stable isotopes in common eider, black-legged kittiwake and northern fulmar: a trophic study from an Arctic fjord. Mar Ecol Prog Ser. 2003;256:257–69. [Google Scholar]

[pone.0333302.ref012] 12.Kilpi M, Lindström K. Habitat-specific clutch size and cost of incubation in common eiders, Somateria mollissima. Oecologia. 1997;111:297–301. [DOI] [PubMed] [Google Scholar]

[pone.0333302.ref013] 13.Munday C, Rose P. Environmental and Social Influences on the Behaviour of Free-Living Mandarin Ducks in Richmond Park. Animals (Basel). 2022;12(19):2554. doi: 10.3390/ani12192554 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0333302.ref014] 14.Agüero ML, Borboroglu PG, Esler D. Trophic Ecology of Breeding White-Headed Steamer-Duck (Tachyeres leucocephalus). Waterbirds. 2014;37(1):88–93. doi: 10.1675/063.037.0111 [DOI] [Google Scholar]

[pone.0333302.ref015] 15.Weller MW. Ecological studies of Falkland Islands’ waterfowl. Wildfowl. 1972;23(23):25–44. [Google Scholar]

[pone.0333302.ref016] 16.Fulton TL, Letts B, Shapiro B. Multiple losses of flight and recent speciation in steamer ducks. Proc Biol Sci. 2012;279(1737):2339–46. doi: 10.1098/rspb.2011.2599 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0333302.ref017] 17.Livezey BC, Humphrey PS. Taxonomy and identification of steamer-ducks (Anatidae: Tachyeres). Lawrence, Kan: Museum of Natural History, University of Kansas. 1992. https://www.biodiversitylibrary.org/bibliography/8436 [Google Scholar]

[pone.0333302.ref018] 18.Weller MW. Ecology and behaviour of steamer ducks. Wildfowl. 1976;27:45–53. [Google Scholar]

[pone.0333302.ref019] 19.Johnsgard PA. Ducks, geese, and swans of the world, revised edition. University of Nebraska-Lincoln Libraries. 2010. [Google Scholar]

[pone.0333302.ref020] 20.Agüero ML, Borboroglu PG. Breeding biology of the Chubut Steamer Duck (Tachyeres leucocephalus). Ornitological Neotropical. 2013;24:85–93. [Google Scholar]

[pone.0333302.ref021] 21.Gauthier G. Territorial behaviour, forced copulations and mixed reproductive strategy in ducks. Wildfowl. 1988;39:102–14. [Google Scholar]

[pone.0333302.ref022] 22.Woods RW, Woods A. Atlas of Breeding Birds of the Falkland Islands. Shropshire, England: Anthony Nelson. 1997. [Google Scholar]

[pone.0333302.ref023] 23.Livezey BC, Humphrey PS. Territoriality and Interspecific Aggression in Steamer-Ducks. The Condor. 1985;87(1):154–7. [Google Scholar]

[pone.0333302.ref024] 24.IUCN. Tachyeres brachypterus. The IUCN Red List of Threatened Species. https://www.iucnredlist.org/species/22680047/132524587 2018. Accessed 2025 July 17.

[pone.0333302.ref025] 25.Agüero ML, Borboroglu JPG, Esler D. Nesting habitat of Chubut Steamer Ducks in Patagonia, Argentina. Emu - Austral Ornithology. 2010;110(4):302–6. [Google Scholar]

[pone.0333302.ref026] 26.Cawkell EM, Hamilton JE. The birds of the falkland islands. Ibis. 1961;103A(1):1–27. doi: 10.1111/j.1474-919x.1961.tb02417.x [DOI] [Google Scholar]

[pone.0333302.ref027] 27.Livezey BC. Feeding morphology, foraging behavior, and foods of steamer-ducks (Anatidae: Tachyeres). Museum of Natural History, the University of Kansas. 1989;125:1–41. [Google Scholar]

[pone.0333302.ref028] 28.Nyström KGK, Pehrsson O. Salinity as a constraint affecting food and habitat choice of mussel‐feeding diving ducks. Ibis. 1988;130(1):94–110. doi: 10.1111/j.1474-919x.1988.tb00960.x [DOI] [Google Scholar]

[pone.0333302.ref029] 29.Bakun A, Babcock EA, Santora C. Regulating a complex adaptive system via its wasp-waist: grappling with ecosystem-based management of the New England herring fishery. ICES Journal of Marine Science. 2009;66(8):1768–75. doi: 10.1093/icesjms/fsp073 [DOI] [Google Scholar]

[pone.0333302.ref030] 30.Bakun A. Wasp-waist populations and marine ecosystem dynamics: Navigating the “predator pit” topographies. Progress in Oceanography. 2006;68(2–4):271–88. doi: 10.1016/j.pocean.2006.02.004 [DOI] [Google Scholar]

[pone.0333302.ref031] 31.Van Tussenbroek BI. Plant and frond dynamics of the giant kelp,Macrocystis pyrifera, forming a fringing zone in the Falkland Islands. European Journal of Phycology. 1993;28(3):161–5. doi: 10.1080/09670269300650251 [DOI] [Google Scholar]

[pone.0333302.ref032] 32.Van Der Grient J, Morley S, Arkhipkin A, Bates J, Baylis A, Brewin P. The Falkland Islands marine ecosystem: A review of the seasonal dynamics and trophic interactions across the food web. Advances in Marine Biology. Elsevier. 2023. p. S0065288123000019. [DOI] [PubMed] [Google Scholar]

[pone.0333302.ref033] 33.Pease ML, Rose RK, Butler MJ. Effects of human disturbances on the behavior of wintering ducks. Wildlife Society Bulletin. 2005;33(1):103–12. doi: 10.2193/0091-7648(2005)33[103:eohdot]2.0.co;2 [DOI] [Google Scholar]

[pone.0333302.ref034] 34.Upson R, Lewis R. Updated vascular plant checklist and atlas for the Falkland Islands. Falklands Conservation. 2014. [Google Scholar]

[pone.0333302.ref035] 35.Poncet S. Long-term coastal monitoring of the birds of Stanley Harbour and Cape Pembroke. Island Landcare. 2023. [Google Scholar]

[pone.0333302.ref036] 36.Johnsgard PA. Handbook of Waterfowl Behavior: Tribe Tachyerini (Steamer Ducks). Unknown. 1965. [Google Scholar]

[pone.0333302.ref037] 37.Livezey BC, Humphrey PS. Mechanics of Steaming in Steamer-ducks. The Auk. 1983;100(2):485–8. [Google Scholar]

[pone.0333302.ref038] 38.Calenge C. The package “adehabitat” for the R software: A tool for the analysis of space and habitat use by animals. Ecological Modelling. 2006;197(3–4):516–9. doi: 10.1016/j.ecolmodel.2006.03.017 [DOI] [Google Scholar]

[pone.0333302.ref039] 39.Benhamou S. Dynamic approach to space and habitat use based on biased random bridges. PLoS One. 2011;6(1):e14592. doi: 10.1371/journal.pone.0014592 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0333302.ref040] 40.Fischer JW, Walter WD, Avery ML. Brownian Bridge Movement Models to Characterize Birds’ Home Ranges. The Condor. 2013;115(2):298–305. doi: 10.1525/cond.2013.110168 [DOI] [Google Scholar]

[pone.0333302.ref041] 41.Calabrese JM, Fleming CH, Gurarie E. ctmm: anrpackage for analyzing animal relocation data as a continuous‐time stochastic process. Methods Ecol Evol. 2016;7(9):1124–32. doi: 10.1111/2041-210x.12559 [DOI] [Google Scholar]

[pone.0333302.ref042] 42.Horne JS, Garton EO, Krone SM, Lewis JS. Analyzing animal movements using Brownian bridges. Ecology. 2007;88(9):2354–63. [DOI] [PubMed] [Google Scholar]

[pone.0333302.ref043] 43.Langrock R, King R, Matthiopoulos J, Thomas L, Fortin D, Morales JM. Flexible and practical modeling of animal telemetry data: hidden Markov models and extensions. Ecology. 2012;93(11):2336–42. doi: 10.1890/11-2241.1 [DOI] [PubMed] [Google Scholar]

[pone.0333302.ref044] 44.Michelot T, Langrock R, Patterson TA. moveHMM: an R package for the statistical modelling of animal movement data using hidden Markov models. Methods Ecol Evol. 2016;7(11):1308–15. doi: 10.1111/2041-210x.12578 [DOI] [Google Scholar]

[pone.0333302.ref045] 45.South A, South MA. R Package: rnaturalearth. World Map Data from Natural Earth, Version 01 0 Available online: https://cranr-projectorg/web/packages/rnaturalearth/rnaturalearth.pdf (accessed on 12 November 2024). 2017;.

[pone.0333302.ref046] 46.Burnham KP, Anderson DR. Multimodel inference: understanding AIC and BIC in model selection. Sociological Methods & Research. 2004;33(2):261–304. [Google Scholar]

[pone.0333302.ref047] 47.Angelstam PK, Bütler R, Lazdinis M, Roberge JM. Habitat thresholds for focal species at multiple scales and forest biodiversity conservation — dead wood as an example. 2025.

[pone.0333302.ref048] 48.Kellett DK, Alisauskas RT, Mehl KR, Drake KL, Traylor JJ, Lawson SL. Body Mass of Long-Tailed Ducks (Clangula Hyemalis) During Incubation. The Auk. 2005;122(1):313–8. doi: 10.1093/auk/122.1.313 [DOI] [Google Scholar]

[pone.0333302.ref049] 49.Kellett DK, Alisauskas RT. Body-mass Dynamics of King Eiders During Incubation. The Auk. 2000;117(3):812–7. doi: 10.1093/auk/117.3.812 [DOI] [Google Scholar]

[pone.0333302.ref050] 50.Agüero ML, Lorenti E, Minardi G, Agu A, Berrier E, D’Amico V. Incubation pattern of endangered Chubut Steamerduck (Tachyeres leucocephalus) and environmental features: implications for conservation. In Review. 2022. [Google Scholar]

[pone.0333302.ref051] 51.Humphrey PS, Livezey BC. Nest, eggs, and downy young of the white-headed flightless steamer-duck. Ornithological Monographs. 1985;36:944–53. [Google Scholar]

[pone.0333302.ref052] 52.Koskimies J, Lahti L. Cold-hardiness of the newly hatched young in relation to ecology and distribution in ten species of European ducks. Auk. 1964;81(3):281–307. [Google Scholar]

[pone.0333302.ref053] 53.Nye PA. Heat loss in wet ducklings and chicks. Ibis. 1964;106(2):189–97. doi: 10.1111/j.1474-919x.1964.tb03695.x [DOI] [Google Scholar]

[pone.0333302.ref054] 54.Bayley D, Brickle P, Brewin P, Golding N, Pelembe T. Valuation of kelp forest ecosystem services in the Falkland Islands: A case study integrating blue carbon sequestration potential. OE. 2021;6:e62811. [Google Scholar]

[pone.0333302.ref055] 55.Teagle H, Hawkins SJ, Moore PJ, Smale DA. The role of kelp species as biogenic habitat formers in coastal marine ecosystems. J Experimental Marine Biol Ecol. 2017;492:81–98. doi: 10.1016/j.jembe.2017.01.017 [DOI] [Google Scholar]

PERMALINK

Home range and activity budget in the Falkland Steamer Duck (Tachyeres brachypterus)

Alix M I Kristiansen

Alastair MM Baylis

Sébastien AP Dupray

Luc Lens

Heather Q Mathews

Lucy J Mitchell

John P Y Arnould

Roles

Abstract

Introduction

Fig 1. Map showing the study site: Stanley Harbour (51°41’15”S 57°50’15”W, in red) and Bleaker Island (52°12’24”S 58°51’02”W in blue).

Methods

Study site and animal handling procedures

Fig 2. Movement tracks of birds tagged on Stanley Harbour (A) and Bleaker Island (C), with their associated home and core ranges (respectively B and D).

Data analysis

Results

Table 2. Model estimates for each dependent variable in Table 1. * = model averaged estimates. The values represent the 95% interval. Bold numbers show significance. Light grey indicates variables not kept for the averaged modelling and dark grey not included in the modelling.

Home and core ranges

Fig 3. Means and 95% confidence intervals of each predictor within each of the models; A: Home range (sex); B: Core range (sex); C: Home range (breeding status); D: Core range (breeding status); E: Time spent on land.

Fig 4. Means and 95% confidence intervals of each predictor within each of the models F: Time spent foraging, G: Mean daily distance travelled.

Daily travelled distances

Time spent on land

Fig 5. Proportion of time spent on land per breeding status: Chick-rearing individuals (CR), Incubating females (IF), Non-breeding individuals (NB) and Patrolling Males (PM).

Time spent foraging

Fig 6. Proportion of time spent resting (light blue), foraging (green) and travelling (light grey) per breeding status: Chick Rearing individuals (CR), Incubating Females (IF), Non-Breeding individuals (NB) and Patrolling Males (PM).

Discussion

Home and core ranges

Daily travelled distances

Time spent on land

Time spent foraging

Conclusion

Supporting information

Acknowledgments

Data Availability

Funding Statement

References

Decision Letter 0

Lee Cooper

Roles

Author response to Decision Letter 1

Decision Letter 1

Lee Cooper

Roles

Acceptance letter

Lee Cooper

Roles

Associated Data

Supplementary Materials

Data Availability Statement

ACTIONS

PERMALINK

RESOURCES

Similar articles

Cited by other articles

Links to NCBI Databases