12/17/2022 0 Comments Weekly precipitation totals![]() Nest success was high early in the breeding season (60% were successful) when rates of P. downsi, depending on the time of breeding. We found that Little Vermilion Flycatchers were severely affected by P. 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. Studies of sympatric Darwin's finches suggest two potential reasons: parasitism by the invasive parasitic fly Philornis downsi and extreme climatic events. Understanding the reasons for the low breeding success of this species is a prerequisite for developing efficient conservation strategies. Populations of several species of birds endemic to the Galápagos Islands have declined during recent decades, including endemic Little Vermilion Flycatchers (Pyrocephalus nanus). We discuss the possible ecological mechanisms that could allow for such a mixed strategy. However, younger flies also occurred during the cool season suggesting that some fly reproduction occurs when host availability is low. This study showed that significantly older flies were present towards the end of the cool season, with ~ 5% of captured females exhibiting estimated ages greater than seven months. downsi captured during and between bird-breeding seasons. We tested the hypothesis that adult flies could survive from one bird-breeding season until the next by using a pterin-based age-grading method to estimate the age of P. In the dry lowlands, this fly persists over a seven-month cool season when availability of hosts is very limited. The bird-parasitic fly Philornis downsi has invaded the Galapagos Islands and is causing high mortality of Darwin’s finches and other bird species, and the mechanisms by which it was able to invade the islands are of great interest to conservationists. In tropical environments, host availability is often linked to rainfall, and adaptations of parasites to dry periods remain understudied. Many parasites of seasonally available hosts must persist through times of the year when hosts are unavailable. ![]()
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