PHENOTYPIC CORRELATES OF BREEDING STATUS IN FEMALE CARRION CROWS (CORVUS-CORONE-CORONE) AND HOODED CROWS (CORVUS-C-CORNIX)

Linear body size and plumage characters are relevant to various social and sexual aspects of bird life. In carrion crows, size is related to the individuals' position in the dominance hierarchy which, in turn, influences the chances of acquiring a territory and of breeding. In th is study, 22 osteological and plumage linear measurements in breeding and non-breeding females are compared in two populations of the carrio n crow (Corvus corone corone) and the hooded crow (Corvus corone corni x). Breeding individuals significantly differed from non-breeding ones in several morphological features and scored higher averages in almos t all of them. Discriminant analysis revealed that breeding and non-br eeding females were separated in the multivariate space of morphologic al variables and furnished an efficient classification criterion of sp ecimens. Principal component analysis indicated that the chances of be coming a breeder increase with size. Nesting for female crows is stric tly correlated with fitness, since nest parasitism is likely to be rar e. Hence, larger female crows of both morphs attain a higher fitness t han smaller ones. Linear body measurements and, to a lesser extent, pl umage characters have been shown to be highly heritable in birds. This implies that a potential evolutionary response to selection in terms of increased body size exists in the two crow populations studied whic h, however, might be balanced by other selective pressures acting in o ther parts of the life cycle of crows.