Southern Fulmars Molt Their Primary Feathers while Incubating

Abstract

Molt-breeding overlap and the extent of molt of primary feathers were studied in the Southern Fulmar (Fulmarus glacialoides) in relation to breeding status, sex, breeding experience, and age. Primary molt was observed among breeders and nonbreeders during the incubation period. Nonbreeders renew more feath- ers than breeders. In breeding individuals, males and females renew the same number of feathers. No dif- ference in primary molt score was found between in- experienced and experienced breeders. However, the extent of primary molt was significantly related to age among breeders; older birds had less new feathers than younger birds. These results suggest that primary molt- breeding overlap in Southern Fulmars is a consequence of high food availability during the short summer and a reallocation of energy into molt during incubation. Possible reasons for differences in molt extent owing to age and breeding status are discussed.