An experimental study on the effects of an introduced parasite in Darwin’s finches

• Published in: Biological conservation 2006, Vol.127 (1), p.55-61
• Main Authors: Fessl, B., Kleindorfer, S., Tebbich, S.
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Conservation, protection and management of environment and wildlife; Ectoparasitism; Fledging success; Fundamental and applied biological sciences. Psychology; Galápagos; General aspects; Growth rate; Haemoglobin; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking
• ISSN: 0006-3207; 1873-2917
• DOI: 10.1016/j.biocon.2005.07.013

It is widely recognised that the main threats to the biota of the Galápagos Islands stem from newly introduced diseases, plants and animals. Introduced organisms may lead to the rapid extinction of naïve insular populations. Previous research on Galápagos showed that the parasitic larvae of the fly Philornis downsi occurred in virtually all nests of land bird species examined, with high nestling mortality (27% of all broods) in relation to high parasite infestation. In this study, we used an experimental approach to measure the fitness impacts of the fly larvae in two species of Darwin’s finch (Geospizinae). We created parasite-reduced nests by applying a 1% pyrethrin solution to the nest during the early nesting phase, and measured: (1) nestling growth, (2) nestling haemoglobin (Hb) concentration and (3) fledging success. A single insecticide treatment was sufficient to reduce parasite intensity to nearly zero, and revealed reduced mass gain and reduced fledging success in parasitized nests compared to parasite-reduced nests. This is the first experimental study of fitness impacts by Philornis on its host species. The results are discussed in the light of short-term protection measures for nests of rare finch species in the Galápagos archipelago.