Nesting Success and Nesting Height in the Critically Endangered Medium Tree Finch (Camarhynchus pauper)

Birds

Sonia Kleindorfer¹  Lauren K. Common¹  Petra Sumasgutner² 

[1] College of Science and Engineering, Flinders University, Adelaide 5001, Australia;Konrad Lorenz Research Center, Core Facility for Behavior and Cognition and Department of Behavioral and Cognitive Biology, University of Vienna, 4645 Grünau im Almtal, Austria;

关键词: Rattus rattus;    Philornis downsi;    Short-eared Owl;    Smooth-billed Ani;    avian predators;    invasive species;   

DOI  :  10.3390/birds2040032

来源: DOAJ

【 摘 要 】

When different introduced species across trophic levels (parasite, predator) invade island systems, they may pose significant threats to nesting birds. In this study, we measure nesting height and infer causes of offspring mortality in the critically endangered Medium Tree Finch (Camarhynchus pauper), an island endemic restricted to Floreana Island on the Galápagos Archipelago. Considering all nests at which a male built a nest, sang and attempted to attract a female (n = 222 nests), only 10.4% of nests produced fledglings (5% of nests had total fledging success, 5.4% of nests had partial fledging success). Of the 123 nests chosen by a female, 18.7% produced fledglings and of 337 eggs laid, 13.4% produced fledglings. Pairing success was higher for older males, but male age did not predict nesting success. All nests with chicks were infested with avian vampire fly larvae (Philornis downsi). We attributed the cause of death to avian vampire fly if chicks were found dead in the nest with fly larvae or pupae (45%) present. We inferred avian (either Asio flammeus galapagoensis or Crotophaga ani) predation (24%) if the nest was empty but dishevelled; and black rat (Rattus rattus) predation (20%) if the nest was empty but undamaged. According to these criteria, the highest nests were depredated by avian predators, the lowest nests by rats, and intermediate nests failed because of avian vampire fly larvae. In conclusion, there is no safe nesting height on Floreana Island under current conditions of threats from two trophic levels (introduced parasitic dipteran, introduced mammalian/avian predators; with Galápagos Short-Eared Owls being the only native predator in the system).

【 授权许可】

Unknown