Hatching hierarchy but not egg-related effects governs behavioral phenotypes in gull chicks

In many bird species that practice parental care, siblings often compete for resources and care provided by their parents, although their strategies differ according to hatching rank and condition. Differences in offspring strategies are generally attributed to hatching order and maternal effects, which are difficult to separate because these effects are often correlated. For example, third-hatched chicks of large gull species receive more egg testosterones and corticosterone, which influence early behavioral patterns. In this study, we carried out a cross-fostering experiment with first- and last-laid eggs of the yellow-legged gull (Larus michahellis) to test whether the within-brood variation in behavioral strategies for competing with siblings and coping with stress are due to maternal effects or to hatching order. Chicks hatched in the last position within the experimental brood emitted more chatter calls to attract parents’ attention, were less prone to respond to warning of danger...

在诸多存在双亲抚育行为的鸟类物种中，同胞雏鸟常会争夺亲代提供的资源与抚育照料，但其竞争策略会随孵化顺位与自身状态发生变化。后代竞争策略的差异通常被归因于孵化顺序与母体效应（maternal effects），但由于这两类效应往往存在相关性，因此难以将其区分。例如，大型鸥类的第三只孵化雏鸟会获得更多的卵睾酮（egg testosterone）与皮质酮（corticosterone），这两类物质会影响雏鸟早期的行为模式。本研究以黄腿鸥（Larus michahellis）的首枚与末枚产卵为实验材料，开展交叉抚育实验，旨在探究同胞间用于竞争资源与应对压力的行为策略差异，究竟源自母体效应还是孵化顺序。在实验窝中最后孵化的雏鸟会发出更多啁啾叫声以吸引亲代注意，且更不易对危险预警做出反应……