Table 1. Foraging and breeding performance of Adélie penguins in four seasons.
Values shown are estimates (with 95% confidence interval) based on linear mixed-effect models for foraging behavior and means ± SD or single observations for others.
| 2010/11 | 2011/12 | 2012/13 | 2016/17 | |
| Sea-ice cover | Yes | Yes | Yes | No |
| Foraging behavior | ||||
| Trip duration (hours) | 19.3 (15.9–23.7) | 19.7 (12.4–31.4) | 15.0 (9.0–25.1) | 11.8 (7.6–18.4) |
| Trip distance (km) | 2.1 (1.6–2.7) | 2.4 (1.4–4.3) | 2.4 (1.3–4.5) | 6.9 (4.1–11.9) |
| (N = 91 trips from 15 birds) | (N = 92 trips from 28 birds) | (N = 64 trips from 17 birds) | (N = 260 trips from 27 birds) | |
| Dive duration intercept (s)* | 69 (58–80) | 74 (48–100) | 81 (56–106) | 54 (30–79) |
| (N = 531 dives from 8 birds) | (N = 485 dives from 9 birds) | (N = 1119 dives from 15 birds) | (N = 2275 dives from 19 birds) | |
| No. of krill captured in a 100-s dive |
4.1 (2.8–6.1) | 3.6 (1.4–9.2) | 5.2 (2.2–12.6) | 5.4 (2.2–13.2) |
| (N = 443 dives from 8 birds) | (N = 374 dives from 9 birds) | (N = 996 dives from 15 birds) | (N = 1211 dives from 12 birds) | |
| Body condition | ||||
| Adult female body mass (kg) | 3.8 ± 0.4 (N = 21 birds) | 4.0 ± 0.4 (N = 18 birds) | 4.2 ± 0.3 (N = 29 birds) | 4.4 ± 0.5 (N = 42 birds) |
| Adult male body mass (kg) | 4.4 ± 0.3 (N = 21 birds) | 4.2 ± 0.4 (N = 28 birds) | 4.6 ± 0.4 (N = 42 birds) | 4.9 ± 0.5 (N = 31 birds) |
| Breeding status | ||||
| Chick growth rate (g day−1) | 67 ± 14 (N = 14 birds) | 69 ± 20 (N = 15 birds) | 76 ± 16 (N = 33 birds) | 102 ± 8 (N = 18 birds) |
| No. of nests (in late December) |
70 | 109 | 181 | 108 |
| No. of fledglings (in early February) |
37 | 88 | 219 | 143 |
| Stomach content | ||||
| Prey composition by mass† | Krill 38 ± 46% | Krill 37 ± 46% | Krill 91 ± 19% | Krill 94 ± 14% |
| Fish 62 ± 46% | Fish 63 ± 46% | Fish 9 ± 19% | Fish, 6 ± 14% | |
| Krill composition by mass | E. superba 32 ± 24% | E. superba 73 ± 42% | E. superba 81 ± 34% | E. superba 100% |
| E. crystallorophias 68 ± 24% | E. crystallorophias 27 ± 42% | E. crystallorophias 19 ± 34% | ||
| (N = 10 birds) | (N = 10 birds) | (N = 11 birds) | (N = 8 birds) |
*Intercept of dive duration as a function of dive depth (i.e., dive duration of a hypothetical 0-m dive).
†In addition to krill and fish, a few amphipods (<1% by mass in most birds) were often found.