Non-breeders as a buffer against environmental stress : declines in numbers of great skuas on Foula, Shetland, and prediction of future recruitment
Non-breeders as a buffer against environmental stress : declines in numbers of great skuas on Foula, Shetland, and prediction of future recruitment
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非繁殖者作为应对环境压力的缓冲：设得兰群岛富拉岛的大贼鸥数量下降以及未来招募的预测
DOI：
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发表时间：
1992
期刊：
影响因子：
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通讯作者：
R. Furness
中科院分区：
文献类型：
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作者：
N. Klomp;R. Furness
1.在1988年和1990年繁殖季节（2400和2340 AOT，分别占北方人口的20%），通过计算明显被占领的领土（AOT），设得兰群岛的富拉繁殖大贼鸥Catharacta贼鸥的数量。2.减少的首选食物，sandeels Ammodytes marines的可用性，一直伴随着AOT略有下降，繁殖成年人的觅食努力大幅增加，繁殖成功率下降了75%，表明食物短缺使人口处于压力之下。3.提出了两种方法，允许非繁殖的大贼鸥频繁Foula的数量估计，根据个别colorringed鸟类的研究。共有3303（SE = 243）和4013（SE = 479）非繁殖大贼鸥估计频繁Foula在1989年和1990年繁殖季节，分别。由于每只鸟在殖民地的平均停留时间只有16-21天，因此这些总数远远大于个体数量。4.自1977年以来，繁殖者的数量和非繁殖者的峰值数量都有所下降，尽管非繁殖者的峰值数量下降得更多（非繁殖者减少了80%，繁殖者减少了21.5%）。非繁殖者数量的迅速减少似乎是由于成年存活率降低导致的招募增加，因为首次繁殖和繁殖成功的年龄在1987年之前没有改变。5.由于自1987年以来的育种成功率仅为之前平均水平的25%，我们预测，自20世纪70年代中期以来，富拉非育种者数量的急剧减少将很快导致招募数量的迅速减少，在未来几年内，育种数量将进一步快速下降。6.这项研究支持Porter和Coulson（1987年）的建议，即海鸟群中非繁殖者的数量可能提供对种群产生不利影响的环境变化的早期和敏感的指示，因为非繁殖者对这种压力起着缓冲作用。
1. The number of breeding great skuas Catharacta skua on Foula, Shetland, was determined by counting apparently occupied territories (AOTs) during the 1988 and 1990 breeding seasons (2400 and 2340 AOTs, respectively, representing 20% of the northern hemisphere population). 2. A decrease in the availability of the preferred food, sandeels Ammodytes marines, has been accompanied by a slight fall in AOTs, a considerable increase in foraging effort of breeding adults and a 75% fall in breeding success, indicating that food shortage has put the population under stress. 3. Two methods are presented which allow the number of non-breeding great skuas frequenting Foula to be estimated, based on studies of individually colourringed birds. Totals of 3303 (SE = 243) and 4013 (SE = 479) non-breeding great skuas were estimated to frequent Foula in the 1989 and 1990 breeding seasons, respectively. These totals are far greater than indicated by individual counts, due to each bird staying in the colony an average of only 16-21 days. 4. Both the number of breeders and the peak number of non-breeders have declined since 1977, although the peak number of non-breeders decreased much more (non-breeders by 80%, breeders by 21.5%). The rapid decrease in numbers of non-breeders appears to be due to increased recruitment as a consequence of a reduction in adult survival rate, since age at first breeding and breeding success did not change before 1987. 5. Because breeding success since 1987 has been only 25% of the previous average, we predict that the dramatic reduction in the number of non-breeders at Foula since the mid-1970s will soon be followed by a rapid reduction in recruitment, and a further and much faster drop in breeding numbers, over the next few years. 6. This study supports the suggestion of Porter & Coulson (1987) that numbers of non-breeders at seabird colonies may provide an early and sensitive indication of environmental changes having adverse effects on the population, since non-breeders act as a buffer to such stress.