Sombre Greenbul

The sombre greenbul (Andropadus importunus) is an inconspicuous but extremely vocal bulbul of dense vegetation in eastern and southern Africa. Adults are about 15–18 cm long and weigh around 26 g. Both sexes look alike, with dull olive-green upperparts, olive-grey underparts, a black bill and striking pale whitish eyes. Juveniles have brown eyes, a paler bill and a yellowish eye-ring.

Several other greenbuls share its subdued olive plumage, but the very pale eye is an excellent field mark in adults; similar species generally have darker eyes or more contrasting head and underpart patterns. Even where common, sombre greenbuls are often identified by voice before they are seen because they spend so much time inside thickets and leafy canopies.

Sombre greenbuls occupy coastal scrub, forest and forest edges, dense thickets in wooded valleys, riverine vegetation and several types of woodland. They are strongly associated with dense woody cover, including thickets along drainage lines in otherwise drier landscapes.

The species also uses alien thickets and well-wooded suburban gardens. This gives it some tolerance of modified landscapes, but it is much less characteristic of open country where continuous shrubs, trees and sheltered foliage are absent.

The diet is broad. Fruit and berries are important, together with insects and other invertebrates, including small snails. Birds also take succulent leaves, flowers, unopened buds and aloe nectar, allowing them to switch among seasonal food sources.

Most foraging occurs in the canopy and dense foliage, where sombre greenbuls pick food from leaves and branches. They sometimes descend into the understorey or leaf litter and may make short aerial sallies after flying insects before returning quickly to cover.

Sombre greenbuls are resident and normally encountered singly or in pairs, with larger non-breeding gatherings forming mainly where food is exceptionally abundant. They are shy in dense cover but become conspicuous when singing from the top of a tree or bush to advertise a territory. The loud, repeated song is one of the characteristic sounds of southern African thickets.

A SAFRING study published in 2014 found very high site fidelity among adults and limited dispersal among juveniles, together with regional differences in body size and moult. Annual survival among adults was on average more than twice that of juveniles. Sombre greenbuls are therefore predominantly sedentary forest and thicket birds rather than regular long-distance migrants.

In southern Africa egg laying can occur from October to April, with a strong peak from October to December. Sombre greenbuls are monogamous and territorial solitary nesters. The female builds a rather flimsy open cup of twigs, rootlets, grass, lichen and other plant material, normally up to about 4 m above ground and often attached to supporting twigs with spider web.

Clutches contain one to three eggs. The female incubates alone for about 12–13 days while the male brings her food. Both parents feed and brood the chicks, which leave the nest after roughly 10–14 days and may continue receiving food for up to three weeks. Adults can perform a broken-wing distraction display when the nest is threatened, and nests are frequently parasitized by Jacobin cuckoos (Clamator jacobinus).

The sombre greenbul is classified as least concern on the IUCN Red List and remains common through much of its broad eastern and southern African range.

Its ability to use several woodland, thicket and suburban habitats gives it some resilience to landscape change, although dense woody cover remains central to its ecology and local populations can be reduced where thickets and forest margins are extensively cleared.