Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR 97331-3803, USA.
Proc Natl Acad Sci U S A. 2010 Jul 6;107(27):12375-80. doi: 10.1073/pnas.1000623107. Epub 2010 Jun 21.
High survival and breeding philopatry was previously confirmed for the Adélie penguin (Pygoscelis adeliae) during a period of stable environmental conditions. However, movements of breeding adults as a result of an unplanned natural experiment within a four-colony meta-population provided interesting insights into this species' population dynamics. We used multistate mark-recapture models to investigate apparent survival and dispersal of breeding birds in the southwestern Ross Sea during 12 breeding seasons (1996-2007). The natural experiment was facilitated by the temporary grounding of two immense icebergs that (i) erected a veritable fence separating colonies and altering migration routes and (ii) added additional stress by trapping extensive sea ice in the region during 5 of 12 y. Colony size varied by orders of magnitude, allowing investigation of apparent survival and dispersal rates in relation to both environmental conditions and colony size within this meta-population. Apparent survival was lowest for the smallest colony (4,000 pairs) and similar for the medium (45,000 pairs) and large colonies (155,000 pairs), despite increased foraging effort expended by breeders at the largest colony. Dispersal of breeding birds was low (<1%), except during years of difficult environmental conditions when movements increased, especially away from the smallest colony (3.5%). Decreased apparent survival at the smallest colony could reflect differences in migration chronology and winter habitat use compared with the other colonies, or it may reflect increased permanent emigration to colonies outside this meta-population. Contrary to current thought, breeding penguins are not always philopatric. Rather, stressful conditions can significantly increase dispersal rates.
高存活率和繁殖回游性曾在稳定的环境条件下被证实适用于阿德利企鹅（Pygoscelis adeliae）。然而，在一个由四个群体组成的元种群中，由于一次计划外的自然实验，繁殖成鸟的运动为该物种的种群动态提供了有趣的见解。我们使用多状态标记-重捕模型，调查了在 12 个繁殖季节（1996-2007 年）期间，罗斯海南部海冰上繁殖鸟类的明显存活率和扩散情况。这个自然实验是由两块巨大冰山的暂时搁浅促成的，（i）竖起了一道真正的屏障，将殖民地隔开，并改变了迁徙路线；（ii）在 12 年中的 5 年里，在该地区困住了大量海冰，从而增加了额外的压力。殖民地的大小相差几个数量级，这使得我们可以在这个元种群中调查环境条件和殖民地大小与明显存活率和扩散率的关系。尽管在最大的殖民地，繁殖者付出了更多的觅食努力，但最小的殖民地（4000 对）的明显存活率最低，中等大小（45000 对）和大的（155000 对）殖民地的存活率相似。繁殖鸟类的扩散率很低（<1%），除了在环境条件困难的年份，扩散率增加，特别是从小的殖民地（3.5%）。最小的殖民地的明显存活率降低可能反映了与其他殖民地相比，迁徙时间和冬季栖息地利用的差异，或者可能反映了向这个元种群以外的殖民地的永久性移民增加。与目前的观点相反，繁殖企鹅并不总是回游性的。相反，压力条件会显著增加扩散率。
