Old Age and Breeding Behavior in a Tropical Passerine Bird Ploceus cucullatus under Controlled Conditions

Abstract

Abstract Many tropical species of passerine birds have potentially long reproductive lives in both nature and aviaries, but rate of breeding by old individuals may eventually decline. A group of individually color-banded African Village Weavers (Ploceus cucullatus), a polygynous species, was kept in aviaries at Los Angeles for 22 years. At 14-18 years of age, old males built significantly fewer nests per year, displayed to females less often, had fewer mates, and generally fathered fewer clutches than did the same males when 9-13 years old. One male reached 24 years of age, when he rarely sang and no longer wove when provided with nest materials. The females, after reaching "middle age" (9-13 yr), laid significantly fewer eggs per year, and still fewer during "old age" (14-18 yr). When 14 or more years old, weavers of both sexes rested much more than did young adults 4-6 years old in the same aviary. Individuals differed greatly in the decline of breeding behavior with age. Some individual Village Weavers bred at a surprisingly great age for passerine birds, e.g. fertile copulations by one 19-year-old male and by one 18-year-old female. These seem to be the oldest breeding ages yet recorded for any small passerine bird. Long reproductive life of a small number of individuals that contribute disproportionately to the next generation would give a selection pressure for longevity, and also could help explain the evolution of small clutch size (2-3 eggs) in the Village Weaver and in many other tropical birds.