Feeding on the wing: hovering in nectar-drinking Old World birds—more common than expected

Abstract

A long-standing paradigm in pollination biology is that New World hummingbirds hover and Old World birds perch when visiting flowers to consume nectar. In contrast, it is now known that hummingbirds perch whenever possible and that nectarivorous Old World birds sometimes hover. However, no overview of hovering behaviour and its frequency in nectarivorous Old World birds exists. This review documents observations of hovering behaviour in 81 species in 11 families of Old World birds, mainly in sunbirds (46 species) and other specialist nectarivores, and less frequently in generalist nectarivores. Hovering behaviour occurs more frequently than thought, not only in terms of the range of avian species but also in its occurrence within species. It was found that neither the geographical distribution of bird species nor their traits (size, body mass) are a limiting factor for hovering behaviour, but that plant traits are important. When perches at the plants are inadequate or lacking, hovering is more appropriate or necessary. It is suggested that, as to foraging behaviour, the distinction between specialist and generalist nectarivorous birds is more adequate than that between hovering hummingbirds and perching passerines. In other words, the foraging behaviour of specialist nectarivorous passerines is more similar to that of hummingbirds than to that of generalist passerines.

Additional keywords:

• African birds
• behavioural ecology
• flight
• foraging
• generalists
• nectarivory
• ornithophily
• perching
• pollination
• specialists
• sunbirds