Variation in egg-size in the Wedge-tailed Shearwater (Puffinus pacificus)
Darren R. Peck A B C , Carol A. Erwin A and Bradley C. Congdon AA School of Tropical Biology, James Cook University, PO Box 6811, Cairns, Qld 4870, Australia.
B Present address: Laboratoire d’Ecologie Marine ECOMAR, Université de la Réunion, 15, Avenue René Cassin, BP 7151, 97715, St Denis, Réunion, France.
C Corresponding author. Email: darren.peck@jcu.edu.au
Emu 106(3) 227-231 https://doi.org/10.1071/MU05037
Submitted: 14 July 2005 Accepted: 16 June 2006 Published: 18 August 2006
Abstract
We assessed variation in the size of eggs of Wedge-tailed Shearwaters (Puffinus pacificus) within and between two colonies in eastern Australia. Eggs at Heron Island were significantly larger than at Lord Howe Island. We also found significant between-season variation in size of eggs at Heron Island, with larger eggs being laid in 2005 than 2006. Mean female size (as indicated by tarsal length) did not differ between the two colonies, or between seasons at Heron Island. However, as with other seabird species, larger females produced larger eggs. Overall, our results imply that facultative changes in female reproductive effort associated with changes in availability of resources are not the main cause of variation in egg-size in this species. The consistently smaller size of eggs for birds at Lord Howe Island compared with those from Heron Island suggests that obligate processes (e.g. natural selection) are more likely to be responsible.
Acknowledgments
Our sincere thanks to the following people and institutions that provided logistic assistance during this project: Y. Peck, T. Wilson, S. Thompson, I. Hutton, D. Wilcox, C. Bagnato, the staff of the Heron Island Research Station, and the Lord Howe Island Board. This research was funded by a James Cook University Merit Research Grant (MRG-02/0026), The Ecological Society of Australia, Reef CRC and Australian Geographic. Work was authorised under New South Wales NPWS Licence number S10914, QNPWS Permits C6/000175/00/SAA and C6/000195/01/SAA, and James Cook University-Ethics Approval A627_00.
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