WASHINGTON, April 16 (Xinhua) -- The larger crest a male auklet has, the more suitable the seabird is to be a mate, U.S. researchers reported on Thursday.

    The study, published in the Journal of Comparative Physiology B, indicates that the size of males' crests may be more than simple ornamentation, providing an explanation of why female auklets prefer males with larger crests.

    Hector Douglas, from the University of Alaska Fairbanks, said his team studied the small, sooty-gray seabirds during fieldwork on Big Koniuji of the Shumagin Islands in the Aleutian Chain, Alaska, in 2002.

    Blood samples taken from the seabirds showed that larger crests correlated with lower levels of corticosterone, a type of stress hormone, in the males' bloodstream, and Douglas said these male seabirds coped better with the stresses of reproduction, such as finding food, competing with other birds for nest sites, and helping rear chicks.

    "Theoretically males that have a lower level of stress hormone have a greater capacity to respond to additional stress," Douglas said.

    "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," he said.

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