Hamerkop

Characteristics

Hamerkops are named for their unique head shape, which resembles a hammer thanks to a pointed wedge of feathers on the back of the head. Their large beak is flattened in shape and has a small hook at the end of the upper mandible. Both genders display solid, dusky brown feathers.

Species Specifics

The hamerkop is devided into two subspecies: Scopus umbretta minor and S. umbretta umbretta. The minor subspecies is restricted in range to coastal areas of West Africa from Senegal to Nigeria, while the umbretta subspecies is much more widespread and occurs from the Arabian paeninsula to the Western Cape and on Madagascar.

Physical Characteristics

These wading birds have long, bare legs with partially webbed toes that aid them in hunting in shallow waters. Their long bills and necks allow then to pluck prey out of the water without submerging their heads.

Ecology

Habitat

Wetlands, Riparian area, forests and woodlands. Occasionally more arid semi-deserts.

Distribution

A hamerkop pair will usually occupy a well-defined territory that they rarely leave, though some will move seasonally into wetter habitat suitable for breeding and utilize drier habitat during the rest of the year. These movements are between adjacent habitats, and the species is considered non-migratory.

Diet

Hamerkops feed on frogs and tadpoles, small fish, small mammals, and aquatic invertebrates. Their distribution closely correlated with that of the Xenopus genus of frogs, suggesting that they are reliant on Xenopus as a major food source.

Ecological Web

Carnivorous. Hamerkops are wading birds like storks and herons and forage for food in shallow water, where they may stir the water with their feet or flap their wings to startle prey. They can also hunt on the wing, dipping down to grab a fish out of open water. They often get robbed of their prey by larger birds like the Fish Eagle. Hamerkop’s large nests are utilized by many other members of their ecosystem in a variety of ways. Smaller birds, such as weaver birds, mynas, and pigeons will sometimes attach their own small nests to the main nest. Unused nests are quickly taken over by other hole-nesting birds like the Egyptian goose or knob-billed duck, and some more aggressive birds such as the Verreaux’s eagle owl and Gray kestrel will sometimes evict a hamerkop pair from an active nest and take over. Despite their large and carefully constructed nests, about 50% of all hamerkop eggs are lost to predators such as monitor lizards and snakes.

Activity and Behavior

Activity Pattern

Hamerkops are not considered migratory, but some pairs will move between adjacent habitats seasonally. Nesting and breeding behavior will occur in riparian areas, and more arid habitats can be utilized during non-breeding times.

Behavior

Hamerkops are very resourceful in their hunting techniques. They are known to hunt while perched on the back of a hippo, giving them access to deeper water than they cannot wade in. They will also follow a cattle or buffalo herd as they graze, preying on the insects that get flushed out.

Social Behavior

Hamerkops are monogamous in their breeding behavior, but are often found congregating in groups of 8-10 individuals outside of the breeding season. Groups can occasionally reach over 50 individuals.

Reproductive Behavior

Individuals will gather near nesting sites for social courtship displays, where many birds start calling all at once while running around each other in circles with crests raised and wings fluttering. False copulation may occur during these displays, but true mating does not occur until a paid has begun building their nest. Once a mated pair has been established, hamerkops are monogamous and will build a massive, domed nest that will be used for several years. The male and female build the nest together, collecting up to 8,000 twigs and other items that weigh at least 25kg when complete. The enormous cave-like nest is accessed only by a single small, narrow entrance hole.

Offspring

Females lay 3-7 eggs, of which about half usually survive predation to hatch. The male and female will both feed the chicks until they fledge at about 50 days. Chicks will often continue to return to their nest for two weeks after their first flight, and may roost together in the nest for another month before dispersing.

Conservation

Status

Listed as a species of Least Concern by the IUCN. Not listed under CITES.

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