Ligon Russell A, Hill Geoffrey E
Department of Biology, Auburn University, AL 36849.
Anim Behav. 2010 Mar;79(3):727-734. doi: 10.1016/j.anbehav.2009.12.028.
Males typically have greater variance in reproductive success than females, so mothers should benefit by producing sons under favorable conditions. Being paired with a better-than-average mate is one such favorable circumstance. High-quality fathers can improve conditions for their offspring by providing good genes, good resources, or both, so females paired to such males should invest preferentially in sons. Ornamentation has been linked to male quality in many birds and, in support of differential allocation theory, females of several avian species invest more in entire broods when paired to attractive mates. Additionally, the females of some bird species apparently manipulate the primary sex-ratio of their broods in relation to the attractiveness of their mates. However, empirical support for a link between mate ornamentation and preferential feeding of sons (another form of biased investment) is lacking. We tested for correlations between sex-biased parental investment and mate plumage colour in the eastern bluebird (Sialia sialis), a species in which juveniles have sexually dichromatic UV-blue plumage. We found that the proportion of maternal feeding attempts to fledgling sons (versus fledgling daughters) was positively correlated with structurally coloured plumage ornamentation of fathers. Additionally, paternal feeding attempts to sons were correlated with plumage ornamentation of mothers and increased in fathers exhibiting breast plumage characteristics typical of older males. These results provide further support for the idea that parental strategies are influenced by mate attractiveness and provide the first evidence that mate ornamentation can influence parental behavior even after offspring have left the nest.
通常情况下，雄性在繁殖成功率上的差异比雌性更大，所以在有利条件下母亲生育儿子会更有利。与高于平均水平的配偶配对就是这样一种有利情况。高质量的父亲可以通过提供优良基因、优质资源或两者兼而有之来改善其后代的生存条件，因此与这类雄性配对的雌性应该优先投资于儿子。在许多鸟类中，羽饰与雄性质量有关，而且为了支持性别差异分配理论，一些鸟类物种的雌性在与有吸引力的配偶配对时，会对整个一窝幼鸟投入更多。此外，一些鸟类物种的雌性显然会根据配偶的吸引力来操纵其一窝幼鸟的初级性别比例。然而，缺乏关于配偶羽饰与优先喂养儿子（另一种形式的偏向投资）之间联系的实证支持。我们对东部蓝鸲（Sialia sialis）进行了性别偏向性亲代投资与配偶羽色之间相关性的测试，东部蓝鸲的幼鸟具有两性异形的紫外蓝色羽毛。我们发现，母亲对幼鸟儿子（相对于幼鸟女儿）的喂食尝试比例与父亲结构色羽饰呈正相关。此外，父亲对儿子的喂食尝试与母亲的羽饰相关，并且在具有典型老年雄性胸部羽色特征的父亲中有所增加。这些结果为亲代策略受配偶吸引力影响这一观点提供了进一步支持，并首次证明即使在后代离巢后，配偶羽饰也能影响亲代行为。
