Department of Evolution, Ecology, and Behavior, School of Integrative Biology, University of Illinois Urbana-Champaign, Urbana, IL, USA.
Illinois Natural History Survey, Prairie Research Institute, University of Illinois Urbana-Champaign, Champaign, IL, USA.
Oecologia. 2021 Apr;195(4):861-872. doi: 10.1007/s00442-021-04888-w. Epub 2021 Mar 12.
Avian obligate brood parasites lay their eggs in the nests of other species that may provide care for the foreign offspring. Brood parasitism often imparts substantial fitness losses upon host nestlings when they are raised alongside the typically more competitive, larger, and older parasitic chick(s). Whereas fitness costs due to reduced host offspring survival in parasitized broods have been studied in detail, the physiological changes in host nestlings caused by parasitic nestmate(s) are less well known. We compared prothonotary warbler (Protonotaria citrea) nestlings, a host of the nest-sharing brown-headed cowbird (Molothrus ater), in experimentally parasitized vs. non-parasitized broods. Our aim was to determine whether cohabitation with brood parasitic young impacted host nestling baseline corticosterone plasma concentrations, immune responses, body condition, and mortality. Corticosterone levels and body condition of host nestlings were similar between nests with or without a cowbird nestmate, whereas host immune responses were lower and nestling mortality was greater in parasitized broods, irrespective of variation in brood size or total brood mass. We detected no trade-offs of baseline corticosterone levels with either immune responses or with body condition. These results suggest that this host species' nestlings experience some adverse fitness-relevant physiological effects in parasitized broods, but are also resilient in other aspects when coping with brood parasitism.
鸟类专性巢寄生者将它们的蛋产在其他物种的巢中，这些物种可能会为外来后代提供照顾。当巢寄生的雏鸟与通常更具竞争力、体型更大和年龄更大的寄生雏鸟一起饲养时，巢寄生常常会给宿主雏鸟带来大量的适应度损失。虽然已经详细研究了由于寄生雏鸟存活率降低而导致的宿主后代的适应度成本，但宿主巢雏鸟因寄生巢伙伴而导致的生理变化却知之甚少。我们比较了 Protonotaria citrea 的巢雏鸟（一种共享巢穴的棕色头牛鹂（Molothrus ater）的宿主），这些巢雏鸟在实验性寄生和非寄生的巢中。我们的目的是确定与巢寄生幼体共同生活是否会影响宿主巢雏鸟的基础皮质酮血浆浓度、免疫反应、身体状况和死亡率。无论巢中是否有牛鹂，宿主巢雏鸟的皮质酮水平和身体状况都相似，而寄生巢中的宿主免疫反应较低，巢雏鸟死亡率较高，而不论巢大小或总巢质量的变化如何。我们没有发现基础皮质酮水平与免疫反应或身体状况之间存在任何权衡。这些结果表明，这种宿主物种的巢雏鸟在寄生的巢中经历了一些与适应度相关的不利生理影响，但在应对巢寄生时，在其他方面也具有弹性。
