An evaluation of three field techniques for sexing Gould’s Petrels (Pterodroma leucoptera) (Procellariidae)
T. W. O’Dwyer A D , D. Priddel B , N. Carlile B , J. A. Bartle C and W. A. Buttemer AA School of Biological Sciences, Institute for Conservation Biology, University of Wollongong, NSW 2522, Australia.
B Department of Environment and Conservation (NSW), PO Box 1967, Hurstville, NSW 2220, Australia.
C Museum of New Zealand Te Papa Tongarewa, PO Box 467, Wellington, New Zealand.
D Corresponding author. Email: twodwyer@ucdavis.edu
Emu 106(3) 245-252 https://doi.org/10.1071/MU05058
Submitted: 14 November 2005 Accepted: 3 May 2006 Published: 18 August 2006
Abstract
Many petrels show no obvious sex-linked dimorphism in plumage or size and consequently many researchers fail to sex the living individuals they study. Several methods of sex discrimination that do not rely on plumage- or obvious size-dimorphism can be used to sex live petrels. The effectiveness of three such techniques was evaluated: body condition at the time of laying, cloacal inspection, and discriminant function analysis (DFA) of external morphometrics. Gould’s Petrel (Pterodroma leucoptera leucoptera) was used as the subject species. Sexing of breeding adults on the basis of body condition at laying proved to be highly accurate (100% of birds sexed correctly) but required detailed knowledge of the breeding biology. Following training, cloacal inspection proved to be an accurate (96%) method of determining the sex of breeding adults, but not of chicks. Unlike molecular sexing, the latter two methods of sex discrimination provide immediate knowledge of the sex of individuals in the field. DFA of external morphometrics predicted the sex of adults with an accuracy of 73% and the sex of near-fledged chicks with an accuracy of 66%. However, the probability of correct assignment of sex was low in most cases and, therefore, this is the least useful of the three techniques assessed here.
Acknowledgments
Thanks to Mike Double for providing training in the molecular sexing techniques. Hilar Shamir, Dean Portelli and Hayden Torr assisted with the fieldwork. This project was conducted under NSW National Parks and Wildlife Service (NPWS) Scientific Licences A2635 and A697; Australian Bird Banding Scheme Authorities 8010, 1208, and 1373; NPWS Animal Care and Ethics Approval 021028/02 and University of Wollongong Animal Ethics licence AE00/15. Leg-bands were supplied by the Australian Bird and Bat Banding Scheme. Two anonymous reviewers provided valuable comments on a previous version of this manuscript.
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