New Zealand Journal of Zoology abstracts
A method for determination of gender from bill measurements in Otago blue penguins (Eudyptula minor)
A. G. Hocken*
RD 6-D
Oamaru, New Zealand
email: agh@es.co.nz
J. J. Russell
P.O. Box 220
Oamaru, New Zealand
*
Author for correspondence.
Abstract
Ability to distinguish the gender of individuals of any animal population is a useful field tool. Blue penguins (Eudyptula minor
) exhibit a sexual dimorphism in bill size which has not been confirmed for any New Zealand population solely by internal anatomy. In this study, bill and head dimensions were taken from birds sexed by dissection. Measurements taken from a reference group of morphologically adult birds were used to construct equations by discriminant analysis. Those equations were applied to the bill measurements of a separate, opportunistically collected test sample, including juveniles, the gender of which was known from necropsy. We found a 15% inaccuracy in the test group, mostly derived from errors in identifying juvenile males. Removal of those individuals reduced the error to 10%. Application of the equation to 47 pairs of living birds of a monitored breeding population determined the gender wrongly for only two of 94 birds. Except for juvenile males, this method is useful for identifying gender in unselected populations of blue penguins in the field. The principle is readily applicable to other New Zealand populations.
Keywords
blue penguin; E. minor; gender; bill size
Z01012 Received 2 April 2001; accepted 3 September 2001
New Zealand Journal of Zoology, 2002, Vol. 29
: 63–69
0301–4223/02/2901–0063 $7.00/0 © The Royal Society of New Zealand 2002
PDF file of entire paper: Print-quality (96K)
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