Paternity and paternal behaviour in the red-winged blackbird, Agelaius phoeniceus

Abstract

The relationship between paternity and male parental behaviour was investigated in an eastern population of red-winged blackbirds. Data collected over four seasons revealed substantial variation in paternity and the frequency of male provisioning. The feeding of nestlings by males increased non-linearly with the age of the nestlings but did not differ within or between seasons. Average relative provisioning by males to individual nests was not associated with the proportion of nestlings sired by the territory owner (determined through multi-locus DNA fingerprinting), either in a bivariate analysis or a multivariate analysis with those variables found to be associated with male parental care in other studies of red-winged blackbirds. Males provisioned significantly less frequently at nests of older females, but paternity was not associated with female age. The later in the season a female settled, the higher her mate's paternity in her brood, yet male provisioning was not associated with female settlement date. Estimated total provisioning by males (sum of all feeding trips over all nests in each male's territory) was not associated with average paternity in bivariate and multivariate analyses. Total provisioning by males was positively associated with the number of days in the season the male had a brood in a bivariate test, but not with male age, the number of females nor male condition in either bivariate or multivariate analyses. The lack of a relationship between paternity and paternal effort fits predictions of recent theory on the potential effects of reduced paternity on paternal behaviour given (1) the lack of consistent patterns of paternity among nests of different order, time of season and male and female age and (2) generally weak associations between possible behavioural cues about paternity and actual paternity.