Bigger feather crests in male seabirds reflect their suitability as mates

Washington, Apr 17 (ANI): The size of males' feather crests in a breed of northern seabird is not just simple ornamentation, but a physical indicator of the bird's quality as a mate, according to a study by researchers at the University of Alaska Fairbanks.

For a long time, scientists have known that female auklets prefer males with larger crests, but they have been unaware of the reason behind it to date.

The new study has shown that low levels of stress hormones in males with larger crests indicate that they cope better with the stresses of reproduction, like finding food, competing with thousands of other birds for mates and nest sites, and helping rear chicks.

"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.

The researchers claim that their results fit into a larger theory about animal societies.

Douglas said: "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. The cost of attaining and maintaining dominant status is reflected in the animals' physiology and this has a distinct pattern in the society."

For the study, the researchers examined the small, sooty-gray seabirds during fieldwork on Big Koniuji in the Shumagin Islands in the Aleutian Chain during June and July of 2002.

They captured and measured the auklets at a mountainside colony and collected blood samples.

After analysing the blood samples for the stress hormone corticosterone, it was 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. 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," said Douglas.

The study has been published this month in the Journal of Comparative Physiology B. (ANI)