Hamerkops usually feed alone or in pairs and mainly during the daytime, taking a rest at noon to roost. Their diet consists of mainly aquatic invertebrates and they will also eat fish, insects, shrimp and rodents. They wade through shallow water searching for prey. To flush prey out of hiding, they rake their feet through the water bed or flap their wings to startle what ever is hiding in the mud or under rocks.
Hamerkops have a very strange behaviour that is unlike other birds. Several or more of the birds get together and perform rituals or courtship displays that involve running around each other in circles, fluttering their wings, raising their crests and calling loudly. Another unusual feature is ‘false mounting’. This involves one bird standing on top of another and appearing to copulate, however, neither are mates and copulation does not actually take place.
Another unique feature of the Hamerkop is that, although they are only medium-sized birds, they have huge nests that can measure over 2 metres in depth and width and weigh up to 50 kilograms in weight. These nests are made from 1000’s of sticks, twigs. reeds. grasses and stems of aquatic vegetation held together by mud and are so strong that they could hold the weight of a man. They take around 3 – 6 weeks to complete having been worked on by both members of a pair.Nest walls are built on a sturdy platform and topped with a domed roof. A mud-plastered entrance 13 to 18 centimetres wide in the bottom leads through a tunnel up to 60 centimetres long to a nesting chamber large enough for the parents and their young. The outside of the nests are decorated with bright objects that the birds collect.Nests are often built in the fork of a tree, on a cliff ledge, a water bank, or dam and preferably over a water source. Hamerkops are obssessed with building nests and will construct 3 – 5 nests per year in their territory, whether they are for breeding purposes or not.