Large-crested male seabirds make better partners

April 17th, 2009 - 1:45 pm ICT by IANS  

Washington, April 17 (IANS) The size of male feather crests in a particular breed of northern seabird may be more than a matter of simple ornamentation and mean low levels of stress hormones, according to a new study.
Low levels of stress hormones in males with larger crests indicate that they cope better with the stresses of reproduction, such as finding food, competing with thousands of other birds for mates and nest sites, and helping rear chicks.

Scientists have long noted that female auklets prefer males with larger crests. But until recently, they did not know why.

“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,” said Hector Douglas, assistant professor of biology at the Kuskokwim Campus in Bethel.

Douglas and collaborator Alexander Kitaysky, associate professor at the University of Alaska Fairbanks (UAF) Institute of Arctic Biology, said their results fit into a larger theory about animal societies.

“There appears to be a social hierarchy at the colony which is correlated with the size of the male ornament and this, in turn, is related to the levels of stress hormones,” Douglas said.

Douglas and his field team studied the small, sooty-gray seabirds during fieldwork on Big Koniuji in the Shumagin Islands in the Aleutian Chain during June and July 2002.

They captured and measured the auklets at a mountainside colony and collected blood samples. Kitaysky’s lab analysed the blood samples for the stress hormone corticosterone. They found that larger crests correlated with lower levels of corticosterone in the males’ bloodstream.

“Theoretically males that have a lower level of baseline stress hormone have a greater capacity to respond to additional stress,” Douglas said, according to an UAF release.

These findings were published in the Journal of Comparative Physiology B.

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