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Dropping water levels support breeding

Avatar of inke inke - 25. septembre 2018 - Environment, Gondwana Collection

The lower mandible of the African Skimmer is two to three centimetres longer than the upper one. The birds fly low over the water and “plough” it with the lower mandible. The bill snaps shut as soon as it touches a fish and the prey is tightly sandwiched in-between.

Dirk Heinrich

When the mighty Zambezi River overflows its banks, additional habitats with an abundant food supply are created for many bird species. Young fish thrive in the shallow warm water and countless insect larvae are also found there. For African Skimmers, however, an important habitat is lost: the white sandbanks disappear under the masses of water and with them the sleeping and resting places as well as the nesting sites.

The total population of this bird species in Africa is estimated to be around 10000. In Namibia, this inter-African migrant is found only in the northern parts of the Kavango regions and in the Zambezi Region. African Skimmers are threatened with extinction in southern Africa. Thus it is all the more pleasing to discover nests with eggs, chicks and juveniles in the vicinity of Zambezi Mubala Lodge and Zambezi Mubala Camp. After the level of the Zambezi River dropped by several metres during the last months, many white sandbanks reappeared along the main stream and around the islands.

This chick lies well-camouflaged in the hoof print of a cow. The fledgling birds dig a little depression for themselves and seek shelter there when they are threatened. Pressed flat to the ground they stay put motionless until their parents sound the all-clear.

On a sandbank west of the lodge and the camp a flock of slightly over 50 young skimmers can be seen spending the day there with adult birds. Some ten kilometres downriver a few more of these strange-looking birds are nesting on a white sandbank. At the end of August (2018) there were at least two nests, each with three brown-speckled eggs, on the fine sand and at least three well-camouflaged chicks were seen lying in flat hollows: next to dry cow dung, in a hoof print of a cow and in brownish sand on a sandbank. Fledged juveniles were waiting on the riverbanks for their parents to go fishing again and bring back treats.

African Skimmers have a unique way of fishing. At dusk and at night, and not only in moon-lit nights, these birds skim the surface of the water with their beak open and the lower mandible, which is two to three centimetres longer, partially submerged at an angle of 45 degrees. They “plough” the water for a distance of 50 to 100 metres, then turn and fly the same length again. Their wings never touch the water. When the bill touches a fish it snaps shut in a flash, giving the prey no chance to escape. Fish no bigger than 80 millimetres are caught and eaten this way. An African Skimmer weighs around 160 grams, and the wingspan is a little more than one metre.

The speckled eggs may seem conspicuous in the flat nesting hollow on the white sand, but plant debris and the droppings of other birds have accumulated everywhere on the sandbank. Since the colour is similar the eggs and nests are protected by this excellent camouflage.

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