Tropical Boubou - Description

Description

The Tropical Boubou is fairly large for its family (bushshrikes), measuring 23–25 cm in length. Its weight can vary between about 38-70 g, but typically adults weigh between 50 and 60 g. Females are on average a bit smaller than males, but individual variation is so large that for most practical purposes the sexes seem to be of identical size. The wing measures about 98 mm on average (between 85 and 110), the tail is a mere two millimetres longer both on average and as regards variation. The tarsus is c.29–37 mm long, 33 mm on average, while the bill's exposed culmen measures a little over 20 mm in some populations and as much as 25 mm in others. Unlike the other measurements where there is mostly individual variation, the bill length might distinctly vary between subspecies.

Not only are males and females the same size, they have identical plumage too The adults' upperparts and tail are glossy blue-black except for concealed white spots on the rump, visible only when the wings are spread and the rump feathers are erected. The underparts are white, in some populations with a buffy or pinkish tinge on the breast and flanks, which is not always noticeable except in good light. The wings of most subspecies have a white stripe on the wing coverts, in some extending onto the secondary remiges. The tips of the outer tail feathers can be white in some subspecies. The bill is black, the legs and feet bluish-grey. The irides are dark reddish-brown.

Nestlings have pinkish-brown skin and are nude after hatching, later growing sparse down; they apparently have spots inside their bills which they show their parents to get fed. Fledglings are similar to adults but duller, with the brownish head and the upperparts appearing mottled due to yellowish-ochre to tawny feather tips, forming a barring on the lower back and rump. The wing-stripe, if present, is dulled down. The undertail coverts are buff, and there is usually dusky barring on the dull white underside, especially on the flanks. The bill is greyish-brown above, paler below. Immature birds independent from their parents have lost most of the mottling (except on the wing coverts) and barring, but their wing stripe and underside are still dull white, shading to brown on the flanks; any white tail feather tips appear at this stage.

A melanistic morph of the taxon sublacteus occurs in a small area of coastal Kenya. It is glossy black all over, lacking even the white rump spots.

The northwesternmost populations of major might be confused with Turati's Boubou (L. turatii), which has no white wing-band and a buff chin and white belly, while major around the southern edge of the Congo Basin look almost identical to the Swamp Boubou (L. bicolor), but this is pure white below and its females give a characteristic "ratchet" call in duets. Southeastern birds (mossambicus and especially limpopoensis) resemble the Southern Boubou (L. ferrugineus) but are black above instead of dark brown and grey – though this may be hard to see at a distance and entirely indistinguishable in the occasionally seen hybrid. The melanistic sublacteus morph is hard to distinguish from the sympatric Slate-colored Boubou (L. funebris), but that species is a very dark bluish-grey instead of black. However, even where the "Tropical Boubou" is sympatric with other Laniarius, they are rarely found in the same habitat.