Ecological selection and sexual dimorphism in the sooty oystercatcher, Haematopus fuliginosus
Article first published online: 15 JUL 2011
© 2011 The Authors. Journal compilation © 2011 Ecological Society of Australia
Volume 37, Issue 2, pages 248–257, April 2012
How to Cite
APLIN, L. M. and COCKBURN, A. (2012), Ecological selection and sexual dimorphism in the sooty oystercatcher, Haematopus fuliginosus. Austral Ecology, 37: 248–257. doi: 10.1111/j.1442-9993.2011.02263.x
- Issue published online: 22 MAR 2012
- Article first published online: 15 JUL 2011
- Accepted for publication April 2011.
- Haematopus fuliginosus;
- niche divergence;
- sexual dimorphism
Male and female sooty oystercatchers (subspecies Haematopus fuliginosus fuliginosus; Haematopodidae) have an average difference in bill length of 19%. We studied the relationship between this sexual dimorphism and foraging ecology at coastal sites in southern New South Wales, Australia. Intersexual foraging divergence was most striking in diet, with seven prey classes eaten exclusively by one sex (male: 4, female: 3), and all shared prey classes eaten in different proportions. Intersexual diet partitioning was also observed in energetic rewards gained from foraging, with females gaining highest energetic benefits from eating ascidians and males from eating limpets. Furthermore, within the most commonly consumed prey item, limpets, females gained higher energetic benefit from eating smaller sizes while males gained greater rewards from the largest limpet sizes. Intersexual divergence was also observed in several aspects of foraging behaviour. Finally, there was a significant effect of tidal cycles upon intersexual niche partitioning in this species; the degree of diet divergence varied between tide conditions and females had a consistently more efficient dietary intake on neap tides than males. Diet divergence in the sooty oystercatcher is greater than previously observed in any oystercatcher, and is correlated with the largest sexual bill dimorphism recorded in this family. It is argued that intersexual competition between territorial pairs is operating to diverge male and female bill morphology.