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THE HAMERKOP

14 April 2014

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The hamerkop Scopus umbretta is found near water bodies from the south-western Arabian Peninsula south to Africa and Madagascar except in highly arid regions. The word umbretta is Latin for shade or dusky brown. The sexes are alike in plumage and the adults are some 56 cm tall. The males weigh 535 g as opposed to 475 g in the females. The hamerkop (Afrikaans for hammer head) is completely umber in colour, but darker on the wings and paler on the under parts and throat. The bill is black and has a sharp hook. The eyes are brown and the legs and feet are black. Young birds look like the adults.

Hamerkops are silent when foraging on the ground. They are locally common and sedentary but move to different foraging areas. They inhabit the edges of shallow water bodies and wetlands and rarely occur along coastlines. The hamerkop is usually solitary or occurs in pairs and is active mainly by day. Hamerkops can aggregate in large groups at abundant food resources. They walk with rapid, jerky steps while moving the head and neck back and forth and do not excrete on their legs as storks do in hot weather. Hamerkop pairs do mutual grooming and there is often false mounting with the male getting on to back of a female to stand there and clap his wings vigorously. Up to ten birds may roost together in a bush beside the water, but single birds may roost with cormorants, egrets and Hadeda ibises.

The hamerkop is agile in flight and uses thermals to glide. It dips the bill in water as a displacement behaviour when it is disturbed. Hamerkops forage while flying over or standing along the edge of water. They push the feet alternately into mud or shake the feet in water to disturb prey and snatch it. They also forage from the water surface while flying over water at rapids. The hook on the bill allows a hamerkop to extract prey from vegetation. It sometimes hunts for food from the back of a hippopotamus or accompanies a band of banded mongooses Mungos mungo that forages around a waterhole. It also associates with grazing cattle or the African savanna buffalo to forage for grasshoppers that fly up. Hamerkops mostly eat adult toads or tadpoles of Xenopus (platannas) which has the same distribution pattern as the hamerkop. They also eat small frogs, fishes, insects and aquatic invertebrates such as shrimp, and occasionally small mammals, and scavenge food scraps from fish eagles, crocodiles or even lions.

The hamerkop breeds from July to January, but this varies regionally. It lays three to nine chalky white eggs which are incubated for 26 to 30 days. Nestlings stay in the untidy nest for 45 to 50 days. This nest is built by both sexes and is a characteristic deep pile of sticks in a forked branch that forms a woven frame for the nest chamber. Occasionally the nest is built by several pairs. There is a nesting chamber with an entrance low on one side of the nest. The nest is built mostly at sunrise or sunset and the male brings mud to female who lines the walls and floor of the chamber with it. The nest is often decorated with dried leaves and measures 0.7 to 2.0 m in diameter and is 100 to 200 mm high. The nest chamber is 45 to 60 cm diameter and has a downward-sloping entrance funnel. The same nest may be used for up to four years.

Reference:

Hockey, P A R, W R J Dean and P G Ryan (eds) 2005. Roberts – birds of southern Africa, seventh edition. Cape Town: The John Voelcker Bird Book Fund, pp 603 – 604.

Article by Prof J du P Bothma

 

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