Selection of Bill Size Proportions in the Common Rosefinch (Carpodacus erythrinus)

Publication Type:Journal Article
Year of Publication:1992
Journal:The Auk
Date Published:1992
ISBN Number:00048038
Keywords:Carpodacus, Carpodacus erythrinus, Erythrina, Erythrina erythrina, Fringillidae
Abstract:This study analyzed the multivariate morphological differences between survivors and nonsurvivors over winter in three years in the Common Rosefinch (Carpodacus erythrinus). In addition to the standard selection techniques commonly used, a number of multivariate analyses were employed. Differential survival could not be accounted for by differences in trait means. The variance-covariance matrices of survivors and nonsurvivors were highly significantly different, indicating differences in character relationships between the groups. A principal-components analysis of each matrix revealed that character correlations on the first vector from each matrix differed. Among survivors all characters were positively correlated to the first vector, whereas among nonsurvivors the first vector described bill width in relation to bill length. Therefore, these two characters were chosen and used in a full-quadratic regression model. This analysis showed a positive relationship between survival and the combination of bill length and bill width, resulting in increased variance in bill width. In particular, survivors were characterized by a positive relationship between bill length and bill width, whereas nonsurvivors were characterized by either too broad, or too narrow a bill in relation to bill length. Possible causes behind this variation in bill proportions may be recently altered selection pressures as a consequence of a new habitat, and/or the particular conditions encountered during ontogeny (a purely environmental effect).
Short Title:The Auk
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith