On the use of greater covert moult and pectoral muscle as measures of condition in passerines with data for the great tit parus major

Abstract

This paper describes a measure of protein reserves for small passerines based on the shape of the pectoral muscle, and tests its validity in a population of the Great Tit. It also tests the hypothesis that arrested moult of greater-coverts in juvenile Great Tits reflects protein stress at the time of moult. Of first year females 40.9% showed arrested moult while 17.9% of males did. This difference was highly significant. In females unmoulted greater-coverts correlated significantly and negatively with the pectoral muscle score observed in winter. There was no similarity between daughters and their mothers in the number of unmoulted coverts, although they showed a weak resemblance to their fathers. It is suggested that this may be due to shared environment rather than genetic inheritance. Females declined in weight through the breeding season, and also declined in protein reserves while feeding a brood. Male muscle scores declined through the breeding season (between-individual variation implied) but not while feeding a brood (within-individual variation implied). The differences between the sexes are discussed. © 1991 Taylor & Francis Group, LLC.