. 2016 Oct 6;70(11):2595–2610. doi: 10.1111/evo.13071

Table 1.

Summary of the hypotheses and evolutionary concepts relating to how the relative survival and reproductive benefits of dispersal and philopatry may drive prospecting and floating behavior and, ultimately, cooperative behavior or sociality in vertebrates

				Prediction met in Seychelles warblers
Theory	Principles	Concepts	Predictions relative to philopatry in Seychelles warblers	Prospectors	Floaters	Residents
Benefits of prospecting and floating	Survival benefits: access to food	1. Better access to food outside resident territory	1. Prospectors/floaters are in better condition	No	No
			2. Prospectors/floaters have better access to food	No	No
	Reproductive benefits: improved—current or future—reproduction	2A. Higher likelihood of obtaining a territory	1. Prospectors/floaters are more likely to obtain a territory	Yes	Yes
			2. Prospectors/floaters get a territory further away	Yes	Yes
		2B. Obtaining a better quality breeding position	1. Prospectors/floaters obtain a territory with higher food abundance	No	No
			2. Prospectors/floaters get a less related partner	Yes	No
		2C. Access to extrapair mating	1. Prospecting/floating males fertilize extragroup females	No¹	No¹
			2. Prospecting/floating females are fertilized by an extragroup male	Maybe¹	No¹
			3. Females (mainly) prospect in fertile period	No	N/A
Ecological constraint	Habitat saturation	3. No suitable breeding habitat for independent breeding available	1. Individuals that do not find a vacancy return to resident territory	Yes	No
			2. Vacancies are filled very rapidly	Yes/No²	Yes/No²
			3. Breeding positions are obtained by inheritance only/mainly	No³	No³
Ecological constraints and	Survival benefits: a resident territory	4A. Reduced predation	1. Prospectors/floaters suffer more predation	No	No
survival benefits‐of‐philopatry	provides a “safe‐haven”	4B. Access to food in resident territory	1. Individuals are tolerated in resident territory	Yes	No
			2. Individuals in good quality resident territories are less likely to leave	No	No
			3. Related individuals prospect/float less (nepotism)	No	Yes
			4. Individuals in smaller groups prospect/float less	No	Yes
		4C. Prospecting is energetically costly	1. Prospectors/floaters are in worse condition	Yes	No⁴
			2. Prospectors/floaters have lower survival	No⁴	Yes
			3. Prospectors/floaters are attacked in intruded territory	Yes	Yes
			4. Prospecting/floating is condition dependent	Maybe⁴	N/A
Reproductive benefits‐of‐philopatry	Reproductive benefits: individuals stay in a resident territory for—future, current, or indirect—reproductive benefits	5A. Territory inheritance	1. Resident individuals inherit the territory	No⁵	N/A	Only 8%⁵
		5B. Access to nearby vacancies ( = shifting)	1. Individuals obtain a breeding position nearby resident territory	Yes⁵	N/A	Yes⁵
			2. Individuals with more neighboring territories prospect/float less	No	No
			3. Competitive individuals prospect/float less	No/Yes⁶	No⁶
		5C. Access to own reproduction	1. Individuals obtain parentage in their resident territory	Yes⁷	N/A	Yes⁷
			2. Individuals prospect/float less if opposite‐sex breeder is unrelated	No	N/A
			3. Females prospect/float less than males (more parentage⁷)	No	No
		5D. Individuals can obtain (indirect) benefits from helping	1. Nonhelpers prospect more than helpers	No	N/A
			2. Individuals related to the breeders prospect/float less (kin benefits)	No	Yes

To test whether these concepts may explain subordinate behavior in Seychelles warblers, a set of specific predictions was developed and tested in this study. Prospectors were individuals with a resident territory who made temporary prospecting trips, whereas floaters left a territory permanently to float through the population with no resident territory (note therefore that some predictions only apply to prospectors as specific data are not available for floaters (N/A).

¹Subordinate females sometimes lay eggs sired by an extragroup male (Richardson et al. 2001). It is unclear, however, whether these fertilizations are a result of male pursuits, or females actively prospecting to obtain copulations with extragroup males (although most females prospected outside their fertile period [see Results] suggesting that the primary reason for females to prospect is not extragroup matings). Moreover, extragroup offspring are always sired by dominant males, and egg‐dumping (e.g., by floaters) is absent (Richardson et al. 2001).

²Eikenaar et al. (2009) showed that the median time to occupation of a breeding vacancy was 3.5 days, with a range of 1–20 days. Two vacancies remained unoccupied for more than 3 months.

³No direct evidence, but tendency for individuals in better quality territories being more likely to prospect (P = 0.06–0.08; Table 4) and prospecting seems to occur mainly in periods with high food availability (Supporting Information).

⁴Nonsignificant tendency (see Fig. 1).

⁵Of the 170 individuals that obtained a breeding position, 81 (48%) obtained a position further than two territories away from their last resident territory, 75 (44%) obtained a territory nearby (one or two territories from their last resident territory), and 14 (8%) inherited the resident territory.

⁶Males prospect less than females, but prospecting is independent of age (Table 4); both sexes, however, may be considered “competitive” as both defend a territory. Floating was independent of age and sex.

⁷Forty‐four percent of subordinate females lay an egg, but only one of 55 young was sired by a subordinate male (Richardson et al. 2001, 2002). Subordinate cobreeding females are, however, almost always older (>1 year) subordinates (Kingma et al., unpubl. ms.).