Behavioral Ecology and Sociobiology

, Volume 63, Issue 5, pp 731–739 | Cite as

Love thy neighbour? Social nesting pattern, host mass and nest size affect ectoparasite intensity in Darwin’s tree finches

Original Paper


Social nesting behaviour is commonly associated with high prevalence and intensity of parasites in intraspecific comparisons. Little is known about the effects of interspecific host breeding density for parasite intensity in generalist host–parasite systems. Darwin’s small tree finch (Camarhynchus parvulus) on Santa Cruz Island, Galápagos Islands, nests in both heterospecific aggregations and at solitary sites. All Darwin finch species on Santa Cruz Island are infested with larvae of the invasive blood-sucking fly Philornis downsi. In this study, we test the prediction that total P. downsi intensity (the number of parasites per nest) is higher for nests in heterospecific aggregations than at solitary nests. We also examine variation in P. downsi intensity in relation to three predictor variables: (1) nest size, (2) nest bottom thickness and (3) host adult body mass, both within and across finch species. The results show that (1) total P. downsi intensity was significantly higher for small tree finch nests with many close neighbours; (2) finches with increased adult body mass built larger nests (inter- and intraspecific comparison); (3) parasite intensity increased significantly with nest size across species and in the small tree finch alone; and (4) nest bottom thickness did not vary with nest size or parasite intensity. These results provide evidence for an interaction between social nesting behaviour, nest characteristics and host mass that influences the distribution and potential impact of mobile ectoparasites in birds.


Body mass Darwin’s finches Ectoparasites Nesting aggregation Nest size 



We thank the Galápagos National Park Service and the Charles Darwin Research Station for the opportunity to work on the Galápagos archipelago. This study was generously funded by the Max Planck Institute for Ornithology and the Austrian Academy of Sciences between 2000 and 2002, with awards to S. Kleindorfer, in 2004 by Flinders University through a Research Establishment Grant, Conservation International and the American Bird Conservancy. TAME airlines provided reduced airfare to the Galápagos. All procedures followed the Guidelines for the Use of Animals in Research (Flinders University, Charles Darwin Research Station, and Galápagos National Parks), the legal requirements of Ecuador, and were approved by the Animal Welfare Committee of Flinders University (permit E189). We thank: Carlos Vinueza, Santiago Torres, Gustavo Jiménez, Rebekah Christensen, and Jeremy Robertson for their dedicated field assistance, Hernan Vargas and David Wiedenfeld for logistical support and Frank J. Sulloway for helpful comments on the manuscript.


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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  1. 1.Flinders UniversityAdelaideAustralia
  2. 2.School of Biological SciencesFlinders UniversityAdelaideAustralia

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