Sexual dimorphism in thick-billed murres, Uria lomvia

• Published in: Canadian Journal of Zoology
• Main Author: Stewart, Donald T.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1993
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Northwest Territories; Lancaster Sound; Jones Sound; Uria lomvia; uria
• Online Access: http://dx.doi.org/10.1139/z93-048; http://www.nrcresearchpress.com/doi/pdf/10.1139/z93-048

The pattern of sexual dimorphism in thick-billed murres, Uria lomvia, from the Lancaster Sound – Jones Sound region, Northwest Territories, was examined for weight and 21 skeletal characters. Univariate statistics (Bonferroni-corrected t-tests) indicated that males were significantly larger than females in 6 bill and skull characters. Multivariate statistics also indicated that males had larger bills and skulls than females (based on canonical discriminant analysis), but males were not larger than females in overall body size (as defined by the first principal-components axis). The direction and magnitude of dimorphism were consistent with a hypothesis based on sexual selection as the driving force. In particular, large bill and skull sizes in males are consistent with agonistic behaviours associated with male–male competition for breeding sites and mate guarding.