Sunbirds' tendency to hover: the roles of energetic rewards, inflorescence architecture and rain

Abstract

Although the Old World sunbirds are generally considered to be an ecological analogue of the New World hummingbirds, it is commonly believed that in contrast to hummingbirds, sunbirds perch while feeding. Nevertheless, recent studies have shown that Old World nectarivores hover while feeding more frequently than previously thought, and some Old World plants seem to have adapted to hovering bird pollinators. To reveal the importance of sunbird foraging behavior in nectar acquisition and to test whether this behavior is determined by plant architecture and rain intensity, we focused on the specialized West African pollination system of Impatiens sakeriana and its two major pollinators, the Cameroon sunbird Cyanomitra oritis and the northern double-collared sunbird Cinnyris reichenowi. C. oritis hovered more often than C. reichenowi while feeding on flowers, although both species were observed hovering regularly. For both species, hovering reduced the feeding time, but this reduction and the consequent estimated changes in energetic intake were species-specific. We found that both floral pedicel and peduncle length, as well as precipitation, negatively affected the probability of C. reichenowi hovering but did not have any significant effect on the behavior of C. oritis. Our study demonstrates that hovering behavior is common in the studied sunbird taxa and that plant architecture and environmental factors can influence sunbird foraging behavior. Nevertheless, the extent of hovering versus perching behavior, as well as the effects of biotic and abiotic factors, is species-specific.