Larger Crests Signal Lower Stress in Male Auklets
During the breeding season, male and female crested auklets (Aethia cristatella) grow a distinct group of bristle feathers on the top of their head. Scientists have for some time known that both sexes show a preference for selecting mates with larger crests. Now, a team of researchers from the University of Alaska Fairbanks have discovered that the larger feathers a male crested auklet has, the lower its stress hormones. This suggests that males with larger crests may be better able to cope with the demands of reproduction, foraging, and competition. As a result, they could be better mates than males with smaller crests and higher stress hormones.
Crested auklets are small seabirds that gather to breed in colonies along the coastlines and islands of the Bearing Sea, North Pacific, and Okhotsk Sea. They nest on cliffs, in boulder fields, and on sea-facing talus slopes. Crested auklets are socially monogomous but Hector Douglas, one of the study’s lead authors, noted that females will abandon their current mate in favor of a male with a larger crest:
“Females will divorce shorter-crested mates for the opportunity to mate with longer-crested males. Our study suggests that longer-crested males could contribute more to reproductive success because they have greater capacity to meet the social and physiological costs,” ~ Hector Douglas, University of Alaska Fairbanks.
Douglass and colleagues studied the crested aukets on Big Koniuji in the Shumagin Islands in the Aleutian Chain during June and July of 2002. They collected blood samples from the birds and analyzed them for levels of the stress hormone corticosterone.
“Theoretically males that have a lower level of baseline stress hormone have a greater capacity to respond to additional stress. The males with the larger crests had markedly lower levels of corticosterone and therefore they should be better mates. We suspect that crest size is an outward indicator of intrinsic quality, and the data on hormones appears to confirm this.” ~ Hector Douglas, University of Alaska Fairbanks.
The research was published in the April issue of the Journal of Comparative Pysiology B.
Refs:
- Douglas, H., Kitaysky, A., Kitaiskaia, E., Maccormick, A., & Kelly, A. (2008). Size of ornament is negatively correlated with baseline corticosterone in males of a socially monogamous colonial seabird Journal of Comparative Physiology B, 179 (3), 297-304 DOI: 10.1007/s00360-008-0312-6
- Researchers Tie Crest Size to Seabirds’ Suitability as a Mate (University of Alaska Fairbanks)
Photo © Hector Douglas / University of Alaska Fairbanks. Pair of auklets on a rock on St. Lawrence Island in June of 2007.
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