A hammerhead (also called a hamerkop) is a wading bird with strong, medium-long legs and large eyes. "Hammerhead" might seem like a good name for a woodpecker, but this bird's name comes from the shape of its head and not from its actions. On one end of its head is a big backward-pointing crest, and on the other end is a heavy bill. Between the crest and the bill, the bird's neck joins its head like the handle of a hammer.
Chocolate-brown feathers cover the hammerhead's body, with paler feathers on its chin and throat. The female is similar to the male, but slightly larger. The birds are between 20 and 24 inches (50 and 60 centimeters) long from beak to tail, and they have short tail feathers. Their wingspan is 11.6 to 12.4 inches (29.5 to 31.6 centimeters), and they weigh between 14.6 to 15.2 ounces (415 to 430 grams), a little less than a pound. The largest hammerheads are 22 inches (56 centimeters) tall.
Hammerheads live south of the Sahara Desert in the southern two-thirds of Africa. They are also found on the island of Madagascar and in the southwestern part of the Arabian Peninsula. Some of the birds spread out when dry areas become flooded during the rainy season, but they do not migrate in spring and fall. They are common and familiar birds in the places where they live.
Hammerheads are found in almost all types of wetlands. They feed in the shallow waters of lakeshores, riverbanks, ponds, marshes, wetlands near the ocean, and reservoirs behind dams. They usually use large trees near the wetlands for roosting at night and for nesting, but sometimes they use cliffs or rocky hillsides.
Hammerheads are carnivorous, meat eaters, and they eat many different kinds of animals found in or near water. The prey that they eat varies according to where they live. In south and east Africa, the birds usually catch clawed frogs. In other areas, they are more likely to hunt for small fish. Wherever they live, they also eat shrimp and other crustaceans, small mammals, large insects, worms, and water snails. The hammerheads that live near people sometimes dig around in garbage piles for tasty leftovers.
While wading into shallow water, hammerheads pick their prey from among the plants. They may stir up small animals in the water with their feet, or flick their wings to encourage the prey to move. Sometimes the birds hunt from the air. They capture tadpoles or small fish while flying slowly over the water.
BEHAVIOR AND REPRODUCTION
Hammerheads are usually busy feeding, nest building, or caring for their young during daylight hours, although they are less active during the heat of mid-day. Sometimes they are still out and about at twilight, but they settle down to rest and sleep at night. They often hunt for food alone or in small groups, but occasionally large groups (up to fifty birds) may roost near each other in the trees.
At nesting time, hammerheads defend territories, although the territories overlap. The birds breed during the dry season when the wet areas are shrinking. At that time, the frogs, fish, and other prey, animals they hunt for food, are concentrated in smaller areas, and they are easier to catch than during the rainy season. When the prey animals are close together, the parents are able to find plenty of food for their young.
Hammerhead pairs are famous for the huge nests they build. A nest may weigh as much as 55 pounds (25 kilograms) and be strong enough for a person to stand on it. The fork of a tree is the usual place for a nest. Hammerheads prefer to put their nests about 30 feet (9 meters) off the ground. Occasionally they build their nests on cliffs or even on the ground.
The male and female work together on the nest, usually in the morning and evening. The nest may contain more than 8,000 twigs, branches, and leaves that are stuck together with mud. The birds start with a platform for the floor and then begin work on the thick walls. Many of the nests contain several rooms. The birds leave a small opening in the side with a long tunnel leading into the nest. The tunnel is just big enough for them to go through. When the walls are about 5 feet (1.5 meters) high, the birds add a roof over the top.
Often hammerheads use the same nest year after year, but some pairs build as many as five nests in a season. They may abandon some before they finish building them. While one nest is used for raising young, another may become a place to roost at night. Still other nests may be taken over by other animals. Eagle owls, barn owls, Egyptian geese, lizards, and snakes (including deadly cobras) have all been seen using hammerhead nests. Small birds may attach their nests to the outside of hammerhead nests, and sometimes they even move right in and share a big nest while the hammerheads are still living there.
After a hammerhead pair has finished building their nest, the female lays between three and seven white eggs. Both parents sit on the eggs and care for the young. The eggs hatch after about thirty days, and at first the chicks have downy, pale brown feathers. They begin to fly from the nest about fifty days after hatching.
HAMMERHEADS AND PEOPLE
There are many superstitions, myths, and legends about hammerheads. Some Africans tell stories about how the birds have magical powers to bring bad luck to people. Some say that hammerheads can tell who will be the next person to die just by looking at the person's reflection in the water. When the bird spots the unlucky person, it supposedly calls out three warning cries over the person's home, and then the person dies. Another belief is that something bad will happen to people if hammerheads fly over them. It is also said that a hammerhead can cause a house to melt or be struck by lightning, and that it can cause cattle to become sick. One story says that if a pregnant woman imitates the sound of a hammerhead, her baby will cry continuously with the same sound.
When hammerheads are feeding, sometimes they stop eating and skip around each other, opening and closing their wings and uttering a weird cry. These antics remind people of wicked witches chanting spells. Because of all these legends, people have given hammerheads great respect and have tried to stay away from them.
Hammerheads are not in any danger of extinction (dying out).
FOR MORE INFORMATION
Attenborough, David. The Life of Birds. Princeton, NJ: Princeton University Press, 1998.
Burton, Maurice, and Robert Burton. International Wildlife Encyclopedia, vol. 8. Tarrytown, NY: Marshall Cavendish, 2002.
Cohen, Sharon A. Bird Nests. San Francisco: Collins Publishers, 1993.
del Hoyo, Josep, A. Elliott, and J. Sargatal, eds. Handbook of the Birds of the World. Vol. 1, Ostrich to Ducks. Barcelona: Lynx Edicions, 1992.
Perrins, Christopher, ed. Firefly Encyclopedia of Birds. Buffalo, NY: Firefly Books, 2003.
Perrins, Christopher M., ed. The Illustrated Encyclopedia of Birds. New York: Prentice Hall Editions, 1990.
Rayner, Richard. Umboko and the Hamerkop. Harare, Zimbabwe: Baobab, 1988.
Sinclair, Ian, Phil Hockey, and Warwick Tarboton. Birds of Southern Africa. Princeton, NJ and Oxford, U.K.: Princeton University Press, 2002.
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