Abyssinian ground hornbill

Abyssinian ground hornbill
male
female both at Semliki Wildlife Reserve, Uganda
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Bucerotiformes
Family:	Bucerotidae
Subfamily:	Bucorvinae
Genus:	Bucorvus
Species:	B. abyssinicus
Binomial name
Bucorvus abyssinicus (Boddaert, 1783)

The Abyssinian ground hornbill or northern ground hornbill (Bucorvus abyssinicus) is an African bird, found north of the equator and is one of two species of ground hornbill. The other is the slightly larger southern ground hornbill, they are the largest species of hornbills found in Africa.

Description

A large black, terrestrial hornbill which shows white primary feathers in flight. The adult male has a blue patch of bare skin around the eye with an inflatable patch of bare skin on the neck and throat which is red, apart from the upper throat which is blue. The bill is long and black except for a reddish patch at the base of the mandible. On top of the bill there is a short open ended black casque. The female is similar but smaller with any bare skin being wholly dark blue. Juvenile birds are dark sooty-brown with a smaller bill, with a incipient casque. As the juvenile matures, which usually takes 3 years, it gradually develops the plumage, bare skin colour and casque development of the adults. The total length is 90 to 110 cm (35 to 43 in).^[2]

It reportedly averages around 90 to 100 cm (35 to 39 in) tall, around 110 cm (43 in) and weighs approximately 4 kg (8.8 lb). Per Stevenson and Fanshawe, the Abyssinian is a larger species on average than the southern ground hornbill, at 102 cm (40 in), but published weights and standard measurements contrarily indicate the southern species is indeed slightly larger.^[3][4]

Voice

A deep booming uh-uh, uh-uh-uh which is far carrying and is normally made at dawn from either a perch or from the ground.^[2] The male and female sing in duets.^[5]

Habitat

The Abyssinian hornbill is found in open habitats such as savanna, sub-desert scrub, and rocky areas, preferring short vegetation which enables its visual foraging technique. The areas inhabited by this species are usually drier areas than the preferred habitat of the Southern ground hornbill. It will tolerate disturbed areas but does require large trees to be used as nest sites.^[5]

Distribution

The Abyssianian ground hornbill is found in Northern sub-Saharan Africa from southern Mauritania, Senegal and Guinea east to Eritrea, Ethiopia, north western Somalia, north western Kenya and Uganda.^[6]

Abyssinian ground hornbills were also introduced to North America, where they are possibly thriving. ^[7]

Habits

The Abyssinian ground hornbill lives in open grassland, in pairs or small family parties. The patrol their territory be walking and are reluctant fliers, usually only flying when alarmed.^[2] In captivity, they can live 35–40 years. Diet in the wild consists of a wide variety of small vertebrates and invertebrates, including tortoises, lizards, spiders, beetles, and caterpillars; also takes carrion, some fruits, seeds, and groundnuts. Groups of ground hornbills have territories of 2–100 square miles (5.2–259.0 km²). They are diurnal.

The breeding season of the Abyssinian ground hornbill varies across its range, the West African populations breed in June through to August, Nigerian and Ugandan populations breeding in January, while Kenyan birds breed as late as November. They prefer to nest in large trees with baobabs and palm stumps being preferred, the nest is constructed in a cavity. They have also been recorded nesting in other types of cavities including holes in rocks and man-made cavities such as bee-hive logs or baskets. In the ground hornbills the females are partially sealed in using a mixture of mud and vegetation. In other hornbills the nesting female moult their all flight feathers at once but this is not the case in the ground hornbills. The male prepares the nest by lining the cavity with dry leaves before the female enters and lays a clutch of one or two eggs over around five days. She starts to incubate as soon as the first egg is laid so that the chick which hatches first has a head start in development over its sibling. Incubation of each egg takes between 37 and 41 days, during which time there is no effort to keep the cavity clean and the male is responsible for providing food to the incubating female. The weight of the newly hatched chick is around 70 g (2.5 oz) and the first-hatched grows rapidly at the expense of the second hatched, which will normally die of starvation before it is four days old by which time its sibling can weigh as much as 350 g (12 oz). When the surviving chick is 21 to 33 days old the mother leaves the nest and starts to help in food provision, then after 80 to 90 days chick leaves the nest.^[5]

Abyssinian ground hornbills invest a lot in their offspring and the fledged juveniles will remain with their parents for up to three years. They have a slow breeding rate and an average of one chick is raised to adulthood every 9 years so the adults' investment in each young bird raised is exceptionally high.^[5]

Abyssinian ground hornbills are opportunist feeders which follow ungulate herds and forest fires so that they can prey on small animals which are disturbed by the larger animals or flames. An individual Abyssinian can walk up to 11 km (6.8 mi) in a day, pouncing on and eating animals they come across. They have also been recorded digging for arthropods in the soil and attacking bee hives for honeycomb, they very rarely consume any plant matter. The strong bill is used to capture and overcome the prey before it is eaten.^[5]

Predators, parasites and diseases

Abyssinian ground hornbills are preyed on by large carnivores, such as leopards. Human predation for food is common in some In northern Cameroon and Burkina Faso they are hunted by humans for food. The nests may be preyed upon by smaller terrestrial predators.

The Abyssinian ground hornbill is a known host for the bird lice Bucorvellus docophorus, Bucerophagus productus and Bucerophagus africanus; it is also a host for the nematode Histiocephalus bucorvi and the tapeworms Chapmania unilateralis, Idiogenes bucorvi, Ophryocotyloides pinguis, and Paruterina daouensis. An individual held in captivity but which had been caught in the wild died from an infection of the bacteria Aeromonas hydrophila which is a common pathogen in fish but which had not been recorded from wild Abyssinian ground hornbills before. In North America captive Abyssinian ground hornbills have also been known to die because of West Nile Virus.^[5]

Cultural importance

Abyssinian ground hornbills are not a normal quarry for commercial hunters, although they are not uncommon in captivity in zoos. In some areas the species has cultural significance and hunters may tie the severed head and neck of these birds around their necks in the belief that it helps them stalk their wild ungulate quarry. In some villages the call is often imitated and there are even entire songs based on the male and female duets of Abyssinian ground hornbills.^[5]

Conservation

The Abyssinian ground hornbill does not approach the thresholds to be classified as it has an extremely large range but the population size has not been quantified, although it is not thought that it approaches the thresholds for being classified as Vulnerable and for these reasons the species is evaluated as Least Concern.^[8]

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  A pair at Fort Worth Zoo

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  Female Abyssinian Ground-hornbill in Murchison Falls National Park

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  The species has long eyelashes as seen on this female identified by a blue throat pouch.

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  Egg of Bucorvus abyssinicus MHNT

References

1. BirdLife International (2012). "Bucorvus abyssinicus". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
2. Borrow, Nik; Demey, Ron (2001). Birds of Western Africa. A & C Black. ISBN 0-7136-3959-8.
3. Field Guide to the Birds of East Africa: Kenya, Tanzania, Uganda, Rwanda, Burundi by Stevenson & Fanshawe. Elsevier Science (2001), ISBN 978-0856610790
4. "Birds: Hornbill". San Diego Zoo. Retrieved 16 July 2013.
5. "Krause, B. 2009. "Bucorvus abyssinicus" (On-line), Animal Diversity Web". Animal Diversity Web. Regents of the University of Michigan. Retrieved 14 October 2016.
6. "Northern Ground-hornbill (Bucorvus abyssinicus)". Lynx Edicions. Retrieved 14 October 2016.
7. "Abyssinian ground hornbill: invasives 101". Casey Sanders and Alfred Viola. Retrieved 16 November 2016.
8. "Bucorvus abyssinicus (Abyssinian Ground Hornbill, Abyssinian Ground-Hornbill, Northern Ground-hornbill)". International Union for Conservation of Nature and Natural Resources. Retrieved 14 October 2016.