Frugivory and Polygamy in Birds of Paradise

Abstract

Abstract I studied fruit-feeding by nine species of birds of paradise in Papua New Guinea from July 1978 through November 1980 and gathered 1,187 records of foraging at 31 species of trees and vines from 14 botanical families. Fruit consumed was consistently small-to moderate-sized (mean: 1 cm diameter), but fruit of different species of plants showed high morphological diversity. I classify the fruit of 31 plant species into three morphological groups: capsule, fig, and drupe/berry. Each of the primarily frugivorous birds of paradise was recorded taking fruits from 10-21 plant species, including representatives from each class. The monogamous Trumpet Manucode and Crinkle-collared Manucode were fig specialists. More than 80% of their diet was figs. The polygamous species of paradisaeids were more "generalized" fruit-feeders and took significant amounts of fruit from all three morphological categories. The most important types of fruit among the polygamous birds were capsular species (49% of diet). While fig species were visited by birds from many families, most nonfig trees hosted a narrower range of foragers, and two species of trees, Chisocheton weinlandii (Meliaceae) and Gastonia spectabilis (Araliaceae), were visited only by birds of paradise. The frugivorous habits of birds of paradise are similar in several respects to those of the neotropical cotingids and manakins. It is argued that while frugivory is an important component of the evolution of polygamous arena display in these birds, it cannot, by itself, explain why some birds are polygamous and others monogamous. Frugivory in the tropics is a complex syndrome that offers a number of ecological alternatives that, in turn, promote different behavioral adaptations.