Yewa female data

Many bird species are negatively impacted by obligate avian brood parasites, which lay their eggs in the nests of host species. The Yellow Warbler (Setophaga petechia), which is host to the brood-parasitic Brown-headed Cowbird (Molothrus ater), represents one of the best-replicated study systems assessing antiparasitic host defenses. Over 15 prior studies on Yellow Warblers have used model presentation experiments, where breeding hosts are exposed to models of Brown-headed Cowbirds and other nest threats, to test for defenses unique to this species. Here we present results from our own quasi-replication study of the Yellow Warbler/Brown-headed Cowbird system, which used a novel design compared to previous experiments by conducting acoustic playback treatments only rather than presenting visual models with or without calls. We exposed active Yellow Warbler nests to playbacks of Brown-headed Cowbird chatters, Blue Jay calls (Cyanocitta cristata; nest predator), conspecific “seet” calls (a referential alarm call for brood parasitism risk), conspecific “chip” calls (a generic alarm call), and control Wood Thrush (Hylocichla mustelina) songs during the incubation stage. Similar to previous studies, we found that female warblers seet called more frequently in response to playback of brood parasitic chatter calls and conspecific seet calls but produced more chip calls in response to playback of nest predator calls. However, female Yellow Warblers approached all playbacks to similar distances, which was different from the patterns seen in previous studies. Our study demonstrates the importance of both replicating and also pivoting experimental studies on nest defense behavior, as slight differences in experimental design can elicit novel behavioral responses in the same species.

诸多鸟类类群会受到专性鸟类巢寄生者（obligate avian brood parasites）的负面影响，这类寄生者会将卵产于宿主物种的巢中。作为巢寄生者棕头牛鹂（Molothrus ater）宿主的黄林莺（Setophaga petechia），是目前评估宿主抗寄生防御行为的重复度最高的研究体系之一。此前已有超过15项针对黄林莺的研究采用模型展示实验——即让繁殖期宿主接触棕头牛鹂及其他巢威胁者的模型，以检验该物种特有的防御行为。本研究针对黄林莺-棕头牛鹂研究体系开展了准重复实验，与过往实验相比，本研究采用了全新的实验设计：仅进行声学回放处理，而非展示带或不带鸣啭的视觉模型。在孵化期内，我们对处于活跃繁殖状态的黄林莺巢播放了以下声源：棕头牛鹂鸣叫声、冠蓝鸦（Cyanocitta cristata；巢捕食者）鸣叫声、同种"seet"鸣啭（针对巢寄生风险的特指性告警鸣啭）、同种"chip"鸣啭（通用告警鸣啭），以及对照组声源林鸫（Hylocichla mustelina）鸣唱。与过往研究结果一致，我们发现黄林莺雌鸟在接收到巢寄生者鸣叫声回放及同种"seet"鸣啭回放时，会更频繁地发出"seet"鸣啭；而在接收到巢捕食者鸣叫声回放时，则会发出更多"chip"鸣啭。但与过往研究的结果不同的是，黄林莺雌鸟在所有回放声源下的靠近距离均无显著差异。本研究证实了对巢防御行为的实验研究进行重复与改进的重要性——实验设计的细微差异，即可在同一物种中引发全新的行为响应。