Impacts on a threatened bird population of removals for translocation
David Bain A B and Kristine French AA Institute for Conservation Biology and Law, School of Biological Sciences, University of Wollongong, Wollongong, NSW 2522, Australia.
B Corresponding author. Present address: Eco Logical Australia Pty Ltd, PO Box 106, St Georges Basin, NSW 2540, Australia. Email: davidb@ecoaus.com.au
Wildlife Research 36(6) 516-521 https://doi.org/10.1071/WR07186
Submitted: 7 December 2007 Accepted: 30 June 2009 Published: 29 September 2009
Abstract
The removal of individuals from a population may occur for several reasons and responses of populations will vary depending on the magnitude and nature of the removal and the life history of the species. An understanding of the effects of loss of individuals on these populations, and the mechanism of replacement, will be important to conservation. This may be particularly important where wild individuals are used for the increasingly popular conservation strategy of translocation. During the recent translocation of the endangered eastern bristlebird (Dasyornis brachypterus), two monitoring sites were established in the wild source population, one where removals were to take place and another as a control to assess the impact of the removals on the population. The removal of 44 eastern bristlebirds across 3 years from a single area in the source population had no significant detectable impact in the numbers of individuals surveyed. Individuals that were removed appeared to have been replaced within 6 months of their removal, although to a lesser extent in the later part of the study. The origin of the replacement eastern bristlebirds was unknown and the quick recovery was suggested to be a result of juvenile dispersal, perhaps combined with territory uptake by previously non-territorial and non-calling (thus undetectable) individuals within the population. Such a surplus may be a result of insufficient suitable habitat for population expansion, and will also have implications for monitoring populations of rare and cryptic species. It is also suggested that some territorial species may have several mechanisms that can replace losses of individuals from a population.
Acknowledgements
Ken Russell from the statistical consulting service at the University of Wollongong helped with the statistical analysis of the results. This research was carried out in accordance with animal ethics approval from the University of Wollongong (AE02/10) and scientific permits from the Department of Environment and Heritage, Booderee National Park and the NSW Department of Environment and Climate Change. This work was supported by an ARC Australian Postgraduate Award – Industry scholarship with the NSW Department of Environment and Conservation as the industry partner.
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