Hipfner Mark J, Gaston Anthony J, Storey Anne E
Biopsychology Programme, Memorial University of Newfoundland, A1B 3X9, St John's, Newfoundland, Canada.
National Wildlife Research Centre, Canadian Wildlife Service, 100 Gamelin Boulevard, K1A 0H3, Hull, Quebec, Canada.
Oecologia. 2001 Oct;129(2):234-242. doi: 10.1007/s004420100731. Epub 2001 Oct 1.
Comparative studies of birds suggest that differences in nest-site characteristics, such as between open-nesting and cavity-nesting species, might ultimately underlie much interspecific variation in clutch size and renesting capacity. The "renesting hypothesis" holds that in species that typically enjoy high breeding success because they nest in safe sites, individuals maximize fitness by laying large first clutches early in the season while withholding few resources for renesting attempts. We tested whether differences in nesting habits would be associated with differences in egg size and renesting capacity in razorbills (Alca torda) and Brünnich's guillemots (Uria lomvia), long-lived marine birds of the tribe Alcini (family Alcidae) that lay single-egg clutches. Razorbills nest in a dispersed fashion, often building nests of small stones and other matter in enclosed crevices where their eggs and chicks are safe from avian predators. Brünnich's guillemots nest very densely on exposed cliff ledges and do not build nests. Due to these differences in nesting habits, razorbills experience higher hatching success than Brünnich's guillemots. As predicted by the renesting hypothesis, razorbills laid larger eggs than guillemots, after accounting for differences in adult body mass. Associated with this larger investment in first eggs, razorbills were less likely than guillemots to replace lost eggs, and they took longer to do so. As these results were obtained by experimentally removing eggs from early-laying females, they presumably assessed the tendencies of more capable birds in both species. Data from other colonies and years were consistent with these results. We conclude that differences in nesting habits have led to evolutionary divergence in the investment made in first and replacement eggs by these two closely related species.
对鸟类的比较研究表明，筑巢地点特征的差异，比如露天筑巢和洞穴筑巢物种之间的差异，可能最终是导致窝卵数和再次筑巢能力种间差异的重要原因。“再次筑巢假说”认为，对于那些通常因在安全地点筑巢而繁殖成功率较高的物种而言，个体通过在季节早期产下较大的第一窝卵来最大化适应性，同时为再次筑巢尝试保留较少的资源。我们测试了筑巢习性的差异是否与刀嘴海雀（Alca torda）和厚嘴海鸦（Uria lomvia）的卵大小及再次筑巢能力的差异相关，这两种长寿海鸟属于海雀族（海雀科），每次只产一枚卵。刀嘴海雀以分散的方式筑巢，常常在封闭的缝隙中用小石头和其他材料筑巢，这样它们的卵和雏鸟就能免受鸟类捕食者的侵害。厚嘴海鸦在暴露的悬崖壁架上密集筑巢，且不筑巢。由于筑巢习性的这些差异，刀嘴海雀的孵化成功率高于厚嘴海鸦。正如再次筑巢假说所预测的那样，在考虑成年个体体重差异后，刀嘴海雀产下的卵比厚嘴海鸦的更大。与对第一窝卵的这种更大投入相关的是，刀嘴海雀比厚嘴海鸦更不可能替换丢失的卵，而且替换卵所需的时间更长。由于这些结果是通过从早产雌鸟身上实验性地移除卵而获得的，它们大概评估了两个物种中更有能力的鸟类的倾向。来自其他群落和年份的数据与这些结果一致。我们得出结论，筑巢习性的差异导致了这两个近缘物种在对第一窝卵和替换卵的投入上出现了进化分歧。
