Tag Archives: mandible

Bird of the Week – Week 131 – African skimmer

One of the more unusual looking avian inhabitants of the Caprivi region of northern Namibia, and rare enough to be considered “endangered” in the southern African region, is the African skimmer. The most striking feature about the bird is its bill – red with a yellow tip and with the lower mandible about three centimetres longer than the upper mandible.

1-african-skimmer

With a length of approximately 39 cm, the sexes are alike in plumage colouration and the males are larger than the females. Dark, almost black upper parts and white forehead, throat and under parts are quite distinctive. Eyes are brown; legs and feet, with partially webbed toes, are red.

African skimmer

Inhabiting large open stretches of water with bare sandbanks and sandy islands, the African skimmer is usually found in small groups. Their method of feeding is unusual, and provides the reason for the oddly proportioned bill. The birds feed mainly at night, flying low over the water with body tilted forward, bill open and the lower mandible skimming through the water. Although flying very low, their long wings do not touch the water. On encountering a fish, the bill snaps shut and the fish is caught. What an amazing adaptation!

African skimmer

The call of the African skimmer is a loud “kik-kik-kik”.

The African skimmer is monogamous and their nest is an unlined hollow in the sand, usually on a sandbar. The placement of these nests has contributed to the decline in bird numbers in the recent past as the wake of boats using the waterways washes eggs and chicks from the nests. The female lays a clutch of 2 to 4 pale buff-coloured eggs, which hatch after an incubation period of approximately three weeks.

African skimmer

The scientific binomial for the African skimmer is Rynchops flavirostris; Rynchops from the Greek words for “face” and “bill”, and flavirostris from the Latin for a “yellow bill”. The name thus focuses on the extraordinary bill with which this bird is equipped, which is not surprising at all.

African skimmer

Bird of the Week – Week 87 – African openbill

The side view of the African openbill presents an unusual picture as its large bill appears badly constructed and doesn’t close in the fashion of other birds. There is a clear gap of approximately 6 mm between the upper and lower mandibles, although they meet together at the tip. This rather odd-looking arrangement  is a perfect adaptation to the bird’s diet; they feed mainly on aquatic snails and the bill is ideally shaped to grip the shell and also to extract the mollusk from within.

African openbill

The African openbill is a fairly large bird with a length of approximately 90 cm. Males and females are similar in both size and plumage colouration, being largely black with a glossy mantle and breast of green or purple. The distinctive bill is a brownish-horn colour and is paler towards the base; legs and feet are black; eyes are grey.

The African openbills have a wide range, being found throughout most of Africa south of the Sahara. Their preferred habitats are freshwater  wetlands, marshes, lakes and rivers. They are extremely gregarious birds and we have seen enormous flocks wheeling in the skies above the river system that marks Namibia’s northern border with Angola.

African openbill

The vocalizations of the African openbill consist of loud croaks and hinks, but it also communicates  through the medium of bill clattering. As mentioned, they feed mainly on snails, but also on mussels, frogs, crabs and insects. Typically the openbill will detect a snail by sight and catch it in its bill. It then forces the tip of the lower mandible into the shell and cuts through the strong muscle before extracting the mollusk while holding the shell against the ground with the upper mandible.

African openbill

African openbills nest in colonies, building a platform nest of twigs and reeds, which they line with softer vegetation such as grass and leaves. The nest is built in a tree, usually over water. The female lays a clutch of three or four chalky-white eggs that hatch after an incubation period of approximately 30 days.

African openbill

The scientific binomial of the African openbill is Anastomus lamelligerus; Anastomus from the Greek for a “coming together”, referring to the odd bill, and lamelligerus from the Latin for “a thin metal plate”, apparently referring to the flattened shafts of the bird’s feathers.

African openbill