Additional mating opportunities and male parental care in red-winged blackbirds

Abstract

Abstract. The effort a male expends caring for offspring is expected to be influenced by the availability of additional mates. The effect of unmated females on male parental care was examined in red-winged blackbirds, Agelaius phoeniceus , by removing female parents during the nestling period at two different times of the breeding season: (1) early, when unmated females were still available and (2) late, when all females had settled and additional mates were no longer possible. Many males fed nestlings at experimental nests; however, male parental care was not related to the availability of unmated females. Instead, male parental behaviour seemed to be influenced strongly by the presence or absence of an additional mate in her fertile period. Male red-winged blackbirds only fed offspring when no additional mates were in their fertile period. These results suggest that paternity guarding may have influenced male parental behaviour more than the opportunity to attract additional mates or to rear nestlings to independence.