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.