White-billed Buffalo-Weaver Bubalornis albirostris

Identification. The White-billed Buffalo-Weaver Bubalornis albirostris is white-billed. The adult (photo above) is black, with white feather bases showing through as small patches on the lower back, flanks and sides of breast; a white wing patch is visible in flight. The conical bill is white and swollen in breeding males (photo above, from specimen 90331 in Leiden), otherwise black. The immature bird is dark brown with white mottling on the underparts. This species also has a phalloid organ (exposed in photo above, see also Red-billed Buffalo-Weaver).

Distribution. No subspecies of the White-billed Buffalo-Weaver are recognised. In the past it has been regarded as conspecific with the Red-billed Buffalo-Weaver. It occurs from Senegal across the savanna belt to western Ethiopia and Kenya (see map above, based on Birds of Africa). In 2009 it was recorded from Tanzania for the first time, from Naani Hill Gate, Serengeti National Park.

Habitat. The White-billed Buffalo-Weaver inhabits dry savanna. In West Africa, it is found in very open farmland with patches of scrub, along streams and in belts of thorntrees. White-billed Buffalo-Weaver colonies are often in large trees, in or near villages. It is resident at its nesting colonies; when not breeding, birds forage away the nests but return before sunset to roost in the nest.

Food. The White-billed Buffalo-Weaver feeds on seeds, including crops such as millet; also fruit, grasshoppers, termites, beetles and their larvae, and also small animals such as frogs. They forage on the ground, search for insects in cowpats, and remove ectoparasites like ticks from cattle. Large noisy, feeding flocks may include individuals from several colonies. Chicks are fed on insects.

Breeding. The White-billed Buffalo-Weaver is strongly colonial (eg. photo). In a 50km transect survey in baobab savanna in Senegal, 31 trees had large colonies and 29 trees had small colonies; while in acacia savanna, 214 nests were counted in 24km.

The nest is a large compound structure, >1 m in diameter, containing up to 10 individual nest chambers. It is made of dry thorn twigs and branches, and lined with grass and green leaves. The nest is sometimes solitary. The nest entrance is sometimes surrounded by long thorny twigs sticking out. It is built mainly by the male and both sexes add lining. Males may steal material from neighbours, triggering raucous calling. Nest building activity often follows rainfall. In Tanzania, nests may be abandoned, then re-used in subsequent years.

Eggs (clutch 2-4) are whitish or pale greenish, heavily marked with grey and grey-brown. The female incubates the eggs and feeds the young.

Breeding season
Jul-Sept throughout range; also Oct-Nov in some W African countries, mid Feb-Mar in Ethiopia and Eritrea; nest-building activity apparently stimulated by rainfall

Nest site
in thom trees up to 10 m above ground

Nest building
main structure built primarily by male, often stealing sticks from neighbouring nests, both sexes may add Iining material

Colony size
with up to ten individual nest-chambers

Clutch size
2-4

Egg colour
whitish or pale green to bluish, heavily blotched and spotted with grey and grey-brown (Nigeria), or plain to sparsely spotted with brown (Kenya)

Egg size
average for nine eggs in Nigeria 26.7 x 19.6 mm

Incubation
incubation of eggs by female only, no information on duration of incubation period

Chicks and nestling period
feeding of chicks by female only, no information on duration of nestling period; fledged young fed by both sexes