Smith Henrik G, Bruun Måns
Department of Animal Ecology, Lund University, S-223 62 Lund, Sweden Fax: +46-46-222-4716; e-mail:
Oecologia. 1998 Jun;115(1-2):59-63. doi: 10.1007/s004420050491.
In spite of the fact that hatchling size and energy reserves in birds are affected by egg size, many studies have failed to find an effect of egg size on offspring fitness. One possibility is that this is because they have been performed in areas with high food availability and that effects of egg size on offspring fitness are most apparent in areas of low food availability. To investigate this, egg size,␣offspring mass and survival of European starlings (Sturnus vulgaris) were measured in an agricultural landscape with a low but variable amount of pasture, the preferred foraging habitat of parent starlings. Offspring mass was related to egg size, but egg size explained a declining proportion of the variation in nestling mean mass as nestlings grew older. Offspring survival during the early, but not during the late nestling period was related to egg size. Throughout the nestling␣period, survival was related to the mass of the nestlings. It is suggested that the effect of egg size on␣offspring survival is through the effect of egg size on offspring mass, this effect declining as offspring grow older. Offspring survival during the early part of the nestling period was related to egg size when availability of pasture was low, but not when it was high. However, the interaction was not significant. Selection for␣larger egg size is discussed in relation to the structuring␣of starling populations into sources and sinks.
尽管鸟类的雏鸟大小和能量储备受卵大小的影响，但许多研究未能发现卵大小对后代适合度有影响。一种可能性是，这是因为这些研究是在食物供应充足的地区进行的，而卵大小对后代适合度的影响在食物供应不足的地区最为明显。为了对此进行研究，在一个农业景观中测量了欧洲椋鸟（Sturnus vulgaris）的卵大小、雏鸟质量和存活率，该景观中牧场数量少但变化不定，而牧场是亲鸟椋鸟首选的觅食栖息地。雏鸟质量与卵大小有关，但随着雏鸟长大，卵大小对雏鸟平均质量变化的解释比例在下降。雏鸟早期而非晚期的存活率与卵大小有关。在整个雏鸟期，存活率与雏鸟质量有关。有人认为，卵大小对后代存活率的影响是通过卵大小对后代质量的影响实现的，这种影响随着后代长大而减弱。当牧场可利用性低时，雏鸟期早期的后代存活率与卵大小有关，但当牧场可利用性高时则无关。然而，这种相互作用并不显著。结合将椋鸟种群分为源和汇的结构，讨论了对更大卵大小的选择。
