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 greenbul 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 supercilia, but most are drab, with uniform olive-brown to black plumage. Species with dull coloured eyes often sport contrasting eyerings. 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".