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Journal of BirdLife Australia
RESEARCH ARTICLE

Nest-site utilisation and niche overlap in two sympatric, cavity-nesting finches

James Brazill-Boast A B , Sarah R. Pryke A and Simon C. Griffith A
+ Author Affiliations
- Author Affiliations

A Department of Brain, Behaviour and Evolution, Macquarie University, Sydney, NSW 2109, Australia.

B Corresponding author. Email: james.brazill-boast@mq.edu.au

Emu 110(2) 170-177 https://doi.org/10.1071/MU09045
Submitted: 25 May 2009  Accepted: 22 March 2010   Published: 26 May 2010

Abstract

Determining the relative access of a species to critical limiting resources requires knowledge of the spectrum of their resource utilisation (niche space) and that of potential competitors, and the frequency distribution of resources in the environment. We used this theoretical framework to assess the relative access to nesting sites and the potential for interspecific competition between two sympatric cavity-nesting finches. Gouldian (Erythrura gouldiae) and Long-tailed (Poephila acuticauda) Finches are both estrildid finches with similar ecological requirements, gross morphology and geographical ranges. By measuring the characteristics of all tree-cavities in an area of breeding habitat, and identifying those used by each of the two species, we were able to quantify the relationship between total available variation and variation in use by Gouldian and Long-tailed Finches. Using a likelihood-based method, we found that Long-tailed Finches exhibited a broader niche than Gouldian Finches with respect to available variation, and that these niches overlapped. Using these data we estimated that the effective availability of suitable nesting sites for Long-tailed Finches was 38% greater than for Gouldian Finches. Their relatively specialised niche and overlap with a more generalist competitor has the potential to constrain reproduction for Gouldian Finches, and will have implications for the conservation of remaining populations of this endangered species.


Acknowledgements

We thank Liam Brunner, Josephine Dessmann, Christophe Dufresnes and Nina Svedin for all their help with data collection in the field; Save the Gouldian Fund (Cooranbong, NSW) for providing valuable equipment to the project; and the Shire and residents of Wyndham for their help and hospitality. Funding was provided by the Australian Research Council Discovery (S. R. Pryke) and Linkage Grants (S. R. Pryke and S. C. Griffith), and a Macquarie University Research Excellence Scholarship (J. Brazill-Boast).


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