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Effect of an introduced parasite in natural and anthropogenic habitats on the breeding success of the endemic little vermilion flycatcher Pyrocephalus nanus in the Galápagos
Journal of Avian Biology ( IF 1.7 ) Pub Date : 2020-09-01 , DOI: 10.1111/jav.02438
Célina Leuba 1, 2 , Sabine Tebbich 1 , Erwin Nemeth 3 , David Anchundia 2 , Eileen Heyer 1, 2 , Denis A. Mosquera 2 , Heinz Richner 4 , Maria L. Rojas Allieri 2 , Christian Sevilla 5 , Birgit Fessl 2
Affiliation  

In the Galápagos Islands many endemic bird species, including the emblematic Darwin's finches, show significant declines in population size. The endemic little vermilion flycatcher Pyrocephalus nanus, classified as vulnerable with high extinction risk, is strongly declining and broods regularly fail. We investigated multiple causes for breeding failure by comparing breeding success, infestation intensity by the hematophagous larvae of the introduced parasitic fly Philornis downsi, predation, parental food provisioning rate and prey attack rates as indicators of food availability at three study sites differing in anthropogenic habitat alterations: Alcedo on Isabela Island with its pristine habitat remote from human settlements, El Cura, also on Isabela Island but dominated by farmland, and Mina Roja on Santa Cruz Island, a site highly altered by introduced invasive plant species, mainly the blackberry. To test for the causal role of parasitism, we reduced the number of P. downsi larvae in half the nests at each site on Isabela Island, and used the other nests as control. When infestation intensity was experimentally reduced, both breeding success and food provisioning rates increased significantly in El Cura, but not in Alcedo, where breeding success and food provisioning rates were overall higher and infestation intensity lower than in El Cura. In the very small population of the little vermilion flycatcher in Mina Roja most nests were abandoned during the incubation phase before nests were infested by P. downsi. Mammalian predation played a minor role in brood loss at all three study sites. Our experimental study demonstrates that the recently introduced parasitic fly significantly affects breeding success of an endangered endemic bird species, and suggests that the effects are modulated by natural levels of P. downsi infestation and habitat‐related rates of food provisioning. Conservation measures should include P. downsi control combined with creating and maintaining open foraging areas.

中文翻译:

在自然和人为栖息地中引入的寄生虫对加拉帕戈斯地方性小朱红fly捕蝇草繁殖成功的影响

在加拉帕戈斯群岛,许多特有鸟类(包括标志性的达尔文雀)显示出种群数量的显着下降。被归类为具有高灭绝风险的脆弱性的地方性小朱红色fly蝇(Pyrocephalus nanus)正在急剧下降,育雏经常失败。我们通过比较繁殖成功率,引入的寄生蝇Philornis downsi的嗜血幼虫的侵染强度来调查繁殖失败的多种原因,捕食,父母食物供给率和猎物袭击率作为三个研究地点的食物供应量指标,这些研究地点在人为改变生境的方式上有所不同:伊莎贝拉岛上的Alcedo,其原始栖息地也远离人类住区,El Cura也在伊莎贝拉岛上,但以农田为主,以及圣克鲁斯岛上的Mina Roja(该地被引入的入侵植物物种,主要是黑莓)高度改变。为了测试寄生虫的因果作用,我们减少了P. downsi的数量在伊莎贝拉岛上每个地点的一半巢中放入幼虫,并以其他巢为对照。通过实验降低侵染强度后,El Cura的育种成功率和食物供应率均显着增加,而Alcedo则没有,因为Elcedo的育种成功率和食物供应率总体较高,侵扰强度低于El Cura。在Mina Roja很小的朱红色fly捕蝇器种群中,大多数巢在孵化阶段被抛弃,然后被P. downsi侵染。哺乳动物的捕食在所有三个研究地点的产卵量减少中起次要作用。我们的实验研究表明,最近引入的寄生蝇对濒临灭绝的特有鸟类的育种成功产生了重大影响,并表明其影响受到自然下水平的P. downsi侵扰和与栖息地相关的食物供应速度的调节。保护措施应包括对P. downsi的控制以及创建和维护开放的觅食区。
更新日期:2020-09-01
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