Hadada ibis

Taxonomy and systematics

Tantalus hagedash was the scientific name proposed by John Latham in 1790 who described a specimen that he had collected near "Outeniqualand" east of Mossel Bay. It was later placed in a monotypic genus as Hagedashia hagedash but has since been placed in the genus Bostrychia. Three subspecies are recognized, the nominate form is found south of the Zambezi river and is paler and shorter billed than those of other subspecies. Populations to the north of the Zambezi river and towards the eastern parts of Africa including Uganda, Tanzania, Sudan and Ethiopia are larger and longer billed and designated as B. h. nilotica (Neumann, 1909) while to the west from Senegal to Congo and Kenya the darker brown and more brightly glossed populations are designated as B. h. brevirostris (Reichenow, 1907). A range of intermediate plumages are known and other subspecies such as erlangeri and guineensis have been proposed in the past.

Description

The hadeda is a large (about 76 cm long), grey-to-partly brown species of ibis. Males and females are alike in plumage. It has a narrow, white, roughly horizontal stripe across its cheeks. This is sometimes called the "moustache" though it does not reach the mouth corners. The plumage over the wings has an iridescent purple sheen produced by optical microstructures within the feathers. The bird has blackish legs and a large grey-to-black bill but during the breeding season it has a red culmen on the basal half of the upper mandible. The upper surfaces of the toes are of a similar red during the onset of breeding. The wings are powerful and broad, enabling quick take-offs and easy manoeuvring through dense tree cover.

It has an extremely loud and distinctive "haa-haa-haa-de-dah" call—hence the onomatopoetic name. The call is often heard when the birds are flying or are startled, or when the birds communicate socially, for example early in the morning in residential suburbs. While roosting they produce a single loud "haaaa". When foraging, their contact call is a low growl similar to that made by a young puppy.

Distribution and habitat

The hadeda ibis occurs throughout Sub-Saharan Africa in open grasslands, savanna and wetlands, as well as urban parks, school fields, green corridors and large gardens. This bird occurs in Sudan, Burundi, Ethiopia, Senegal, Uganda, Tanzania, Gabon, Democratic Republic of Congo, Cameroon, Gambia, Kenya, Somalia, Lesotho, Swaziland, Botswana, Mozambique, Zimbabwe, Namibia, and South Africa.

The distribution range of the hadeda has increased in southern Africa by nearly two and a half times in the 20th century following the introduction of trees in parts that were treeless. Irrigation projects may have also helped in their expansion as they appear to need moist and soft soils in which to probe for food.

Ecology

Hadeda ibises roost in groups on trees. They fly out in the mornings with loud calls and return in the evenings with regularity. Hadeda feed on insects, millipedes and earthworms, using their long scimitar-like bill to probe soft soil. They also eat larger insects, such as the Parktown prawn, and also spiders and small lizards. These birds also feed readily on snails and often clear garden beds around residential homes. They are particularly welcomed on bowling and golf greens because they are assiduous in extracting larvae of moths and beetles that feed on the roots of the grass.

Like other ibis species, including spoonbills, and like some other probing feeders such as sanderling and kiwi, hadeda have sensory pits around the tips of their bills. In their foraging for unseen prey, such as shallow subterranean larvae, the pits enable them to locate feeding insects and earthworms.

Hadeda have become very common in many African cities and tolerate the closeness of humans. They are able to judge the direction of gaze of humans and the speed of approach to decide their escape strategies. Hadeda ibises have been involved in several bird-hits at airports in Kenya and South Africa.

Hadeda are monogamous and pair bonds are thought to persist throughout the year. Breeding begins after the rains. In the Cape province, they breed mainly from October to November. The nest is a platform of twigs placed in a major branch of a large tree, typically in a fork, and unlike most ibis species, in spite of their moderately gregarious nature, they do not nest in groups. Both parents take part in incubating the clutch of three to four eggs. Incubation takes about 26 days. The parents feed the young by regurgitating food. Many young birds die by falling off the nest. The survivors fledge in about 33 days.

Conservation status

As the hadeda ibis is widespread and common throughout its large range, it has been evaluated as Least Concern on the IUCN Red List.