Department of Evolution, Ecology, and Behavior, School of Integrative Biology, University of Illinois, Urbana-Champaign, IL, 61801, USA.
Prairie Research Institute, Illinois Natural History Survey, University of Illinois, Urbana-Champaign, IL, 61820, USA.
Anim Cogn. 2022 Oct;25(5):1289-1298. doi: 10.1007/s10071-022-01612-w. Epub 2022 Mar 28.
Communication between parents and dependent offspring is critical not only during provisioning, but also in antipredator contexts. In altricial birds, a top cause of reproductive failure is nest predation, and alarm calls both by parents and chicks can serve to alert others and increase the likelihood of offspring escaping predation. Understanding the factors that determine the strength of parental antipredator responses to different nestling alarm calls can provide insight into parent-offspring recognition. The prothonotary warbler (Protonotaria citrea), a host of the obligate brood parasite, the brown-headed cowbird (Molothrus ater), never rejects cowbird young and raises the parasite together with its own offspring. To determine whether warbler parents learn cowbird nestling alarm calls, we presented experimentally parasitized or non-parasitized parents with playbacks of conspecific warbler, parasitic cowbird, and a harmless heterospecific control, eastern bluebird (Sialis sialis), nestling alarm calls. We recorded the latency to respond and the number of chips given by members of the resident warbler pair. We found that parents were most likely to respond to warbler nestling alarm calls, least likely to respond to bluebird calls, with a statistically intermediate likelihood of responding to cowbird calls. Critically, current and past parasitism status did not affect the likelihood of response to any playback or the number of chips given, however, currently parasitized parents had greater response latencies to playbacks than non-parasitized parents. These results suggest that warbler parents do not learn cowbird alarm calls from breeding experiences and, in turn, that cowbirds may employ a generalized, bet-hedging alarm call.
父母与依赖后代之间的沟通不仅在提供食物时很重要，在防御捕食者时也很重要。在晚成性鸟类中，繁殖失败的一个主要原因是巢捕食，父母和雏鸟的警报声都可以提醒其他动物，增加后代逃脱捕食的可能性。了解决定父母对不同雏鸟警报声的防御捕食反应强度的因素，可以深入了解亲代-后代识别。Protonotaria citrea 是一种专性巢寄生的宿主，即棕色头牛鹂（Molothrus ater），它从不拒绝牛鹂幼鸟，并与自己的后代一起抚养寄生虫。为了确定鸣鸟父母是否学习牛鹂雏鸟的警报声，我们用鸣鸟、寄生牛鹂和无害的异源控制鸟（东方蓝知更鸟（Sialis sialis））的雏鸟警报声对实验性寄生或非寄生的父母进行了回放。我们记录了响应的潜伏期和居住鸣鸟对的成员发出的叫声数量。我们发现，父母最有可能对鸣鸟雏鸟的警报声做出反应，最不可能对蓝鸟的叫声做出反应，对牛鹂的叫声做出反应的可能性在统计上处于中间位置。至关重要的是，当前和过去的寄生状态并不影响对任何回放的反应可能性或发出的叫声数量，然而，当前寄生的父母对回放的反应潜伏期比非寄生的父母长。这些结果表明，鸣鸟父母不会从繁殖经验中学习牛鹂的警报声，反过来，牛鹂可能会发出一种通用的、套期保值的警报声。
