Populations of several species of birds endemic to the Galápagos Islands have declined during recent decades, including endemic Little Vermilion Flycatchers (Pyrocephalus nanus). Understanding the reasons for the low breeding success of this species is a prerequisite for developing efficient conservation strategies. Studies of sympatric Darwin’s finches suggest two potential reasons: parasitism by the invasive parasitic fly Philornis downsi and extreme climatic events. We investigated the role of each in the breeding success of Little Vermilion Flycatchers during three breeding seasons in the agricultural zone of Isabela Island. We found that Little Vermilion Flycatchers were severely affected by P. downsi, depending on the time of breeding. Nest success was high early in the breeding season (60% were successful) when rates of P. downsi prevalence and intensity were low, but nest success was zero and all nests were infested later in the breeding season. Philornis downsi prevalence and intensity increased with increasing temperature. Both low and high levels of rainfall had a negative effect on nest survival. A parasite removal experiment using insecticide confirmed the detrimental effect of the invasive parasite; nests infested with P. downsi had significantly lower nest success than treated nests. Injection of insecticide into nest bases can be an efficient short-term way to increase the nesting success of Little Vermilion Flycatchers, but finding long-term measures to control the P. downsi population is of utmost importance.

中文翻译：

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侵入性寄生蝇 Philornis downsi 正在威胁加拉帕戈斯群岛的小朱红捕蝇器

近几十年来，加拉帕戈斯群岛特有的几种鸟类的种群数量有所下降，包括特有的小朱红捕蝇器（Pyrocephalus nanus）。了解该物种繁殖成功率低的原因是制定有效保护策略的先决条件。对同域达尔文雀的研究提出了两个潜在的原因：侵入性寄生蝇 Philornis downsi 的寄生和极端气候事件。我们在伊莎贝拉岛农业区的三个繁殖季节调查了每种在小朱鹟繁殖成功中的作用。我们发现Little Vermilion Flycatchers受到P. downsi的严重影响，具体取决于繁殖时间。当 P. downsi 的流行率和强度很低，但筑巢成功率为零，所有巢穴都在繁殖季节后期出没。Philornis downsi 流行率和强度随着温度的升高而增加。低水平和高水平的降雨对巢穴的生存都有负面影响。使用杀虫剂进行的寄生虫清除实验证实了侵入性寄生虫的有害影响；被 P. downsi 侵染的巢穴的筑巢成功率明显低于处理过的巢穴。向巢基注射杀虫剂可能是提高小朱蝇筑巢成功率的一种有效的短期方法，但找到控制 P. downsi 种群的长期措施至关重要。Philornis downsi 流行率和强度随着温度的升高而增加。低水平和高水平的降雨对巢穴的生存都有负面影响。使用杀虫剂进行的寄生虫清除实验证实了侵入性寄生虫的有害影响；被 P. downsi 侵染的巢穴的筑巢成功率明显低于处理过的巢穴。向巢基注射杀虫剂可能是提高小朱蝇筑巢成功率的一种有效的短期方法，但找到控制 P. downsi 种群的长期措施至关重要。Philornis downsi 流行率和强度随着温度的升高而增加。低水平和高水平的降雨对巢穴的生存都有负面影响。使用杀虫剂进行的寄生虫清除实验证实了侵入性寄生虫的有害影响；被 P. downsi 侵染的巢穴的筑巢成功率明显低于处理过的巢穴。向巢基注射杀虫剂可能是提高小朱蝇筑巢成功率的一种有效的短期方法，但找到控制 P. downsi 种群的长期措施至关重要。downsi 的筑巢成功率明显低于处理过的巢。向巢基注射杀虫剂可能是提高小朱蝇筑巢成功率的一种有效的短期方法，但找到控制 P. downsi 种群的长期措施至关重要。downsi 的筑巢成功率明显低于处理过的巢。向巢基注射杀虫剂可能是提高小朱蝇筑巢成功率的一种有效的短期方法，但找到控制 P. downsi 种群的长期措施至关重要。