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RESEARCH ARTICLE
Contents Vol 106(2)

Sex determination and sexual size-dimorphism in Southern Giant-Petrels (Macronectes giganteus) from Patagonia, Argentina

S. Copello A D , F. Quintana A B and G. Somoza C
+ Author Affiliations
- Author Affiliations

A Centro Nacional Patagónico (CONICET), (U9120ACF) Puerto Madryn, Argentina.

B Wildlife Conservation Society, New York, NY 10460, USA.

C Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús (IIB-INTECH), CONICET-Universidad Nacional de General San Martín, (B7130IWA) Chascomús, Argentina.

D Corresponding author. Email: scopello@cenpat.edu.ar

Emu 106(2) 141-146 https://doi.org/10.1071/MU05033
Submitted: 28 June 2005  Accepted: 28 March 2006   Published: 19 May 2006

Abstract

We used discriminant analysis of a series of external morphometric measurements, together with confirmation by genetic methods, to develop a simple method to determine the sex of fledgling and adult Southern Giant-Petrels (Macronectes giganteus) in colonies in northern Patagonia. We also described morphometric parameters (bill-length, bill-depth, tarsal length, wing-length, and weight) for different classes of age and sex and analysed differences in size between male and female chicks over the growth period. Southern Giant-Petrels showed conspicuous sexual size-dimorphism, with males being significantly larger than females, this difference being apparent within 8 weeks of hatching. In adults, males were 40% heavier than females and consistently larger in all measurements (% sexual size-dimorphism 5–15%). For fledglings, bill-length was the most dimorphic variable (15.2%). The discriminant analysis of four external measurements correctly identified the sex of more than 90% of adults and fledglings. Bill-length alone was sufficient to predict sex of adults and fledglings and can thus serve as a simple and effective tool for sexing Southern Giant-Petrels.


Acknowledgments

Research was part of wider research on the Southern Giant-Petrel on the Patagonian coast of Argentina funded by the Wildlife Conservation Society, Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT), Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET) and Ecocentro Puerto Madryn. We thank the Dirección de Fauna y Flora Silvestre of Chubut Province for issuing the work permits to capture and handle birds. We would like to thank A. Sapoznikow, N. Suaréz, M. Uhart, A. Sabatini, J. Braun, J. E. Sala, G. Morales, F. Marquez, A. Steinfurth, I. Zimmer and I. Escapa for their help in the field and G.C. López for her technical assistance in the laboratory. Special thanks to J. Owen and R. Vera for logistical help. T. Svagelj, P. Yorio and R. P. Wilson are also acknowledged for their valuable comments on early versions of this manuscript.


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