Birds of Paradise and Mating System Theory — Predictions and Observations

Abstract

The predictions of current theory on the evolution of vertebrate mating systems are compared with field observations on the birds of paradise, including a focal study of four sympatric species. In birds, true lek organisation requires shifts in three aspects of behaviour from the typical monogamous system in which both sexes attend the nest: (I) emancipation of the male from nesting duties, (2) initiation of male display at a fixed court, and (3) spatial clustering of male courts into leks. Information from the birds of paradise supports the notion that male emancipation is associated with small clutch-size. Data on the insectivorous Buff-tailed Sicklebill contradict the notion that male emancipation can only occur in frugivores, although it is evident that typical birds of paradise exhibit a diet combining nutritious fruit with insectivory. Information from the highly frugivorous Trumpet Manucode contradicts the assumption that the species depending most heavily on fruit will show the greatest potential for polygynous mating behaviour. As predicted by theory, the polygynous birds of paradise exhibit a long breeding season and may suffer heavy loss of nests to predators. In the typical polygynous bird of paradise neither females nor food or temtori,al resources are defended by males. Lek mating is correlated to four behavioural syndromes among the males (extreme competition for mates, highly skewed mating success, the presence of subordinates and delayed breeding), in combination with a foraging ecology that promoter high mobility by females, and yet permits foraging from a fixed point by the males tied to the lek for more than six months each year.