Change in beak overhangs of cliff swallows over 40 years: Partly a response to parasites?
Change in beak overhangs of cliff swallows over 40 years: Partly a response to parasites?
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DOI：
10.1371/journal.pone.0263422
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发表时间：
2022
期刊：
影响因子：
3.7
通讯作者：
Brown CR
中科院分区：
文献类型：
--
作者：
Wagnon GS;Pletcher OM;Brown CR
有些鸟类的上颌骨突出，上喙的尖端突出于下颌骨之外，并可能向下弯曲。悬垂部分被认为有助于控制羽毛上的体外寄生虫。鲜为人知的是，在何种程度上的上颌突出不同的空间或时间内的人口相同的物种。殖民悬崖燕子（Petrochelidon pyrrhonota）最近转移到几乎完全使用的人工结构，如桥梁和公路涵洞筑巢，因此已暴露于更高水平的寄生比其祖先的悬崖筑巢地点。我们研究了是否增加体外寄生可能有利于最近的变化，上颌突出的程度。使用标本收集的悬崖燕子从内布拉斯加州西部，美国，跨越40年和现场数据的活鸟，我们发现，上颌悬垂的程度增加了跨年的非线性方式，在2000年后期达到峰值，并与悬崖燕子殖民地的大小呈反比，原因不明。在此期间，雏鸟崖燕身上的跳蚤数量普遍下降。那些有明显悬垂的鸟在巢外的燕蝽较少，但它们的筑巢成功率并不比没有悬垂的鸟高。种内变异的上颌悬在崖燕部分是一致的，它有一个功能性的作用，在打击体外寄生虫。悬突程度的暂时增加可能是崖燕对其相对较新的寄生虫暴露的反应。我们的研究结果表明，这种鸟类的形态特征可以随着时间的推移迅速变化。
Some birds exhibit a maxillary overhang, in which the tip of the upper beak projects beyond the lower mandible and may curve downward. The overhang is thought to help control ectoparasites on the feathers. Little is known about the extent to which the maxillary overhang varies spatially or temporally within populations of the same species. The colonial cliff swallow (Petrochelidon pyrrhonota) has relatively recently shifted to almost exclusive use of artificial structures such as bridges and highway culverts for nesting and consequently has been exposed to higher levels of parasitism than on its ancestral cliff nesting sites. We examined whether increased ectoparasitism may have favored recent changes in the extent of the maxillary overhang. Using a specimen collection of cliff swallows from western Nebraska, USA, spanning 40 years and field data on live birds, we found that the extent of the maxillary overhang increased across years in a nonlinear way, peaking in the late 2000’s, and varied inversely with cliff swallow colony size for unknown reasons. The number of fleas on nestling cliff swallows declined in general over this period. Those birds with perceptible overhangs had fewer swallow bugs on the outside of their nest, but they did not have higher nesting success than birds with no overhangs. The intraspecific variation in the maxillary overhang in cliff swallows was partly consistent with it having a functional role in combatting ectoparasites. The temporal increase in the extent of the overhang may be a response by cliff swallows to their relatively recent increased exposure to parasitism. Our results demonstrate that this avian morphological trait can change rapidly over time.
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影响因子：
6.1
作者：
Brown, Charles R.;Brown, Mary Bomberger;Roche, Erin A.
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