Journal article

Androgens during development in a bird species with extremely sexually dimorphic growth, the brown songlark, Cinclorhamphus cruralis

C Isaksson, MJL Magrath, TGG Groothuis, J Komdeur



In birds, early exposure to androgens has been shown to influence offspring growth and begging behaviour, and has been proposed as a mechanism for the development of sexual size dimorphism (SSD). Sex specific effects during development can occur due to sex-specific allocation of maternal androgens, sensitivity to, or synthesis of, androgens. In addition, maternal hormones have been suggested as a mechanism to skew brood sex ratio. This study uses one of the world's most extreme SSD species, the brown songlark Cinclorhamphus cruralis, to investigate (1) sex-specific differences of androgens in yolk and chick plasma and (2) the relationship between androgens and sex ratio bias. The study revea..

View full abstract

University of Melbourne Researchers


Awarded by NWO Rubicon

Funding Acknowledgements

We would like to thank Per Flodin, Jeroen van Dijk, Erica van Rooij, Maria von Post, and lain Woxvold for field assistance. We are grateful to Ken and Mary McCrabb (Avenel /Wangenella), and Derek McFarland (McFarlands St F/Hay) for allowing us to work on their properties, and Bill and Mary-Anne Butcher of Elmsleigh Station for letting us stay on their property and for logistical support. We would also like to thank the NPWS and Rural Lands and Protection Board in Hay for advice. In the Netherlands we would like to thank, Marco van der Velde for molecular sex determination, Bonnie de Vries and Jelle Boonekamp for lab assistance and advice, and Bonnie also for help with calculations of the hormone concentrations. Tobias Uller kindly commented on the paper. This work was conducted with the approval of the Animal Experimentation Ethics Committee of the Australian National University and the NSW NPWS. The project was funded by a NWO Rubicon fellowship to C.I. (project number 825.07.004).