Tuero Diego T, Fiorini Vanina D, Reboreda Juan C
Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón II Ciudad Universitaria, C1428EGA Buenos Aires, Argentina.
Behav Processes. 2012 Feb;89(2):137-42. doi: 10.1016/j.beproc.2011.10.012. Epub 2011 Nov 24.
Interspecific brood parasites, like the shiny cowbird (Molothrus bonariensis), lay eggs in nests of other species. Shiny cowbird females peck and puncture eggs when they parasitize host nests. This behavior increases the survival of cowbird chicks when they have to compete for food with larger nestmates. However, cowbird chicks may benefit from smaller nestmates as they increase food provisioning by parents and the cowbird chicks secure most extra provisioning. We investigated whether egg-pecking behavior by female shiny cowbirds might be adjusted to the competition that their chicks face in host nests. We found that more host eggs are destroyed per cowbird egg laid in a larger-bodied host (chalk-browed mockingbird, Mimus saturninus, 70-75 g) than a smaller-bodied host (house wrens, Troglodytes aedon, 12-13 g). We also tested egg-pecking preferences in choice experiments with female cowbirds in captivity and found cowbirds presented with eggs in artificial nests pecked first and more frequently, and punctured more frequently the larger egg when this was a host egg, but not when this was a cowbird egg. Our results are partially consistent with the hypothesis that shiny cowbird females adaptively adjust their egg pecking behavior according to the competition that their chicks face in host nests.
种间巢寄生者，如辉拟八哥（Molothrus bonariensis），会在其他物种的巢中产卵。辉拟八哥雌鸟在寄生宿主巢穴时会啄破并刺穿宿主的蛋。当牛鹂雏鸟不得不与体型较大的同巢雏鸟争夺食物时，这种行为会提高牛鹂雏鸟的存活率。然而，牛鹂雏鸟可能会从体型较小的同巢雏鸟中受益，因为它们会促使亲鸟增加食物供应，而牛鹂雏鸟能获得大部分额外供应的食物。我们研究了辉拟八哥雌鸟的啄蛋行为是否会根据其雏鸟在宿主巢穴中面临的竞争情况进行调整。我们发现，与体型较小的宿主（家鹪鹩，Troglodytes aedon，12 - 13克）相比，在体型较大的宿主（白眉嘲鸫，Mimus saturninus，70 - 75克）巢穴中每产下一枚牛鹂蛋，被破坏的宿主蛋更多。我们还在圈养条件下对雌鸟进行了选择实验，测试它们的啄蛋偏好，发现当人工巢中有蛋时，牛鹂会首先且更频繁地啄蛋，并且当较大的蛋是宿主蛋而非牛鹂蛋时，它们会更频繁地刺穿宿主蛋。我们的结果部分支持了这样一种假设，即辉拟八哥雌鸟会根据其雏鸟在宿主巢穴中面临的竞争情况，适应性地调整它们的啄蛋行为。
