Bulbuls are a family, Pycnonotidae, of medium-sized passerine songbirds. Many forest species are known as greenbuls, brownbuls, leaf loves, or bristlebills. The family is distributed across most of Africa and into the Middle East, tropical Asia to Indonesia, and north as far as Japan. A few insular species occur on the tropical islands of the Indian Ocean There are about 130 species in around 24 genera. While some species are found in most habitats, overall African species are predominantly found in rainforest whilst rainforest species are rare in Asia, instead preferring more open areas.
The word bulbul derives from Persian, meaning nightingale, but in English, bulbul refers to passerine birds of a different family.
Bulbuls are short-necked slender passerines. The tails are long and the wings short and rounded. In almost all species the bill is slightly elongated and slightly hooked at the end. They vary in length from 13 cm for the tiny greenbelt to 29 cm in the straw-headed bulbul. Overall the sexes are alike, although the females tend to be slightly smaller. In a few species the differences are so great that they have been described as functionally different species. The soft plumage of some species is colorful with yellow, red or orange vents, cheeks, throat or super cilia, but most are drab, with uniform olive-brown to black plumage. Species with dull colored eyes often sport contrasting eye rings. Some have very distinct crests. Bulbuls are highly vocal, with the calls of most species being described as nasal or gravelly. One author described the song of the brown-eared bulbul as “the most unattractive noises made by any bird”.
Bulbul from Attappadi Plateau
Bulbuls eat a wide range of different foods, ranging from fruit to seeds, nectar, small insects and other arthropods and even small vertebrates. The majority of species is frugivorous and supplement their diet with some insects, whilst there is a significant minority of specialists, particularly in Africa. Open country species in particular are generalists. Bulbuls in the genus Cringer and bristle bills in the genus Bleda will join mixed-species feeding flocks.
The bulbuls are generally monogamous. One unusual exception is the yellow-whiskered greenbelt which at least over part of its range appears to be polygamous and engage in a lekking system. Some species also have all parenting arrangements, where non-breeders, usually the young from earlier clutches, help raise the young of a dominant breeding pair. Up to five purple-pink eggs are laid in an open tree nests and incubated by the female. Incubation usually lasts between 11–14 days, and chicks fledge after 12–16 days.
The traditional layout was to divide the bulbuls into four groups, named Pycnonotus, Phyllastrephus, Criniger, and Chlorocichla groups after characteristic genera (Delicious, 1943). However, more recent analyses demonstrated that this arrangement was probably based on erroneous interpretation of characters
Comparison of DNA cytochrome b sequences found that five species of Phyllastrephus did not belong to the bulbuls, but to an enigmatic group of songbirds from Madagascar instead, and they are now usually referred to as Malagasy warblers. Similarly, sequence analysis of the DNA RAG1 and RAG2 genes suggests that the genus Nicator is not a bulbul either (Beresford et al., 2005). That the previous arrangement had failed to take into account biogeography was indicated by the study of Pasquet et al. (2001) who demonstrated the genus Criniger must be divided into an African and an Asian (Alophoixus) lineage. Using analysis of one nDNA and 2 mtDNA sequences, Moyle & Marks (2006) found one largely Asian lineage and one African group of greenbuls and bristlebills; the golden greenbul seemes to be very distinct and form a group of its own. Some taxa are not monophyletic, and more research is necessary to determine relationships within the larger genera.