Patterns of variation in ornaments of Crested Auklets Aethia cristatella

We investigated patterns of variation of Feather and bill ornaments of Cres ted Auklets Aethia cristatella, a monogamous seabird, based on 963 individu als measured in the years 1990 to 1998. Three prominent ornaments were disp layed: a forehead crest, composed of 11-31 curved feathers averaging about 40 mm in length, bilaterally symmetrical white auricular plumes on the side s of the head behind the eyes, averaging about 30 mm in length, and brightl y coloured semi-circular rictal plates at the corners of the bill. As in ot her putative sexually selected traits, auklet ornaments were more variable across individuals than non-ornamental traits. Crest length and auricular p lume length were positively correlated within individuals but not across ye ars. Among the traits measured there was evidence for slight sexual dimorph ism for the auricular plume and rictal plate ornaments and for culmen lengt h and tarsus (males were slightly larger than females) but not for the cres t ornament. Breeding adult females and males had greater crest and plume or nament expression than non-breeding adults. Paradoxically, females' crests and rictal plates were more variable than males' crests and rictal plates. Based on independent samples, the expression of feather ornaments and ricta l plate varied among years between 1990 and 1998. Crested Auklet ornaments did not vary in concert with the ornaments of Whiskered. Aethia pygmaea and Least Auklets Aethia pusilla during this period. Crested Auklet subadults had smaller ornaments than adults. Based on adults remeasured after an inte rval of one to seven years, the size of individuals' feather ornaments incr eased with age. We found no relationship between auricular plume length and asymmetry. Male auricular plumes and female crests were weakly correlated with body condition.