DOUGLAS III, H.D.; KITAYSKY, A.S.; KITAISKAIA, E.V.; Univ. Alaska Fairbanks; Univ. Alaska Fairbanks; Univ. Alaska Fairbanks: Male ornament size profiles vigor and size of bill armament in a monogamous colonial seabird

We studied correlates of ornamental traits in the Crested Auklet Aethia cristatella, a colonial seabird of the North Pacific, known for mutual sexual selection. Previous studies have shown that an ornamental feather crest on the forehead serves as a signal of dominance, and males and females prefer mates with longer crests. However, previous studies failed to link the feather crest and other ornamental traits with viability indicators such as body condition and survival ability. We used the stress hormone corticosterone (CORT) as a measure of intrinsic quality. We judged lower baseline concentrations of CORT and moderate response to standardized acute stress tests as indicative of better vigor. We captured adult Crested Auklets daily during incubation and early chick rearing and took blood samples at standardized time intervals. There was no seasonal trend in CORT, however there were large differences in CORT between individuals. Baseline CORT was negatively correlated with size of the crest ornament in males and negatively correlated with body condition in females. We found that CORT and bill size together predicted 33% of variation in male crest length but not in females. Previous research has shown that: 1) the bill is a primary weapon in male combat, 2) the crest ornament mediates agonistic interactions. We note that in profile the crest ornament arches over the bill, accentuating its size, and bill size is a likely indicator of fighting ability. Size of the male crest ornament appears to profile vigor and bill size, and we suggest that by extension it may advertise ability to obtain and defend resources.