Lewis S, Sherratt T N, Hamer K C, Wanless S
Department of Biological Sciences, University of Durham, South Road, Durham DH1 3LE, United Kingdom.
Nature. 2001 Aug 23;412(6849):816-9. doi: 10.1038/35090566.
The factors affecting the population dynamics of seabirds have long intrigued biologists. Current data suggest that density-dependent depletion of prey during the breeding season may regulate population size. However, much of the evidence for this has been circumstantial, and the underlying mechanisms are unclear. Here, we show that the per capita population growth rates of northern gannet Morus bassanus at colonies in Britain and Ireland have declined with increasing population size. Furthermore, direct observations reveal that the mean foraging trip duration of breeding gannets is positively correlated with colony size, both among colonies of different sizes in the same year, and within colonies as they change in size. To understand this phenomenon, we have developed a model which demonstrates that disturbance of fish alone can readily generate conditions under which gannets at larger colonies have to travel further to obtain food.
长期以来，影响海鸟种群动态的因素一直吸引着生物学家。目前的数据表明，繁殖季节猎物的密度依赖性消耗可能会调节种群规模。然而，这方面的许多证据都是间接的，其潜在机制尚不清楚。在这里，我们表明，在英国和爱尔兰各殖民地，北方塘鹅（Morus bassanus）的人均种群增长率随着种群规模的增加而下降。此外，直接观察表明，繁殖期塘鹅的平均觅食行程持续时间与殖民地规模呈正相关，无论是在同一年不同规模的殖民地之间，还是在殖民地规模变化时的殖民地内部。为了理解这一现象，我们开发了一个模型，该模型表明，仅鱼类受干扰就能轻易产生这样的条件，即较大殖民地的塘鹅必须远行觅食。
