Bucorvus abyssinicus
northern ground hornbill
(Also: northern ground-hornbill)

Northern ground hornbills (Bucorvus abyssinicus) are found in the Ethiopian region across a wide area of north-central Africa, from southern Mauritania and Guinea in the west to Ethiopia, northwest Somalia, northeast Kenya, and northern Uganda in the east. (Kemp, 2001)

Bucorvus abyssinicus is found in savanna, sub-desert scrub, and rocky areas, preferring short vegetation which facilitates foraging. This species generally inhabits drier areas than southern ground hornbills (Bucorvus leadbeateri). Bucorvus abyssinicus tolerates disturbed areas but does require large trees for nesting sites. (Kemp, 2001)

The two species of ground hornbills, Bucorvus abyssinicus and Bucorvus leadbeateri differ from other hornbills in having an extra neck vertebra (giving them a total of 15), longer legs, thick upper eyelid lashes, and a larger body size. The longer legs adapt them well to their primarily terrestrial foraging method, while other hornbills are mainly arboreal. Northern ground hornbills are black, large-bodied birds average 4000 g in mass and 100 cm in length (Kemp, 2001). They have high, rounded, grooved casques (a bony elaboration of the upper mandible covered with a thin sheath of keratin) that is abruptly truncated distally, and a long, deep, curved beak, which they use to catch and subdue prey (Perrins, 2003). The primaries are white and are highly visible in flight. Northern and southern ground hornbills (Bucorvus leadbeateri) can be distinguished by differences in throat skin coloration and casque shape. Northern ground hornbill males have blue and red throat skin and a blue area around the eye, females have only bare blue skin both around the eye and throat. Southern ground hornbills (Bucorvus leadbeateri) have only bare red skin in both areas, and a smaller, shallower, non-truncated casque. Juveniles have brown feathers and less brilliantly colored throat patches. Northern ground hornbills have a yellowish patch at the base of the upper mandible. (Elbel, 1967; Kemp, 2001; Perrins, 2003)

Northern ground hornbills are monogamous, with males tending to females and young during the incubation stage. (Kemp, 2001)

The breeding season depends on location, with West African populations breeding in June through August, Nigerian and Ugandan populations breeding in January, and Kenyan pairs breeding as late as November. The nest is constructed in a cavity of a large tree, with baobabs and palm stumps being preferred. However, they may also accept rock holes or man-made cavities such as bee-hive logs or baskets as nesting sites. Unlike other hornbills, in Bucorvus species females are not completely sealed into a nesting cavity. Instead, they are only partially sealed in by a mixture of mud and vegetation. They also does not undergo the typical synchronous flight feather molt typical of other incubating female hornbills. Males prepare the cavity by lining it with dry leaves, then the female enters and lays one or two eggs over approximately 5 days. Incubation begins with the first egg, so that one hatchling matures more quickly and grows faster than its nest mates. After 37 to 41 days of incubation, during which nest sanitation is not practiced and the male provides food items to the incubating female, the first egg will hatch, with the second hatching later. Newly hatched chicks weigh approximately 70 g. First-hatched chicks grow rapidly at the expense of the later-hatched sibling, which usually dies of starvation within 4 days, when the older sibling may weigh as much as 350 g. After 21 to 33 days the female will leave the nest to help the male in food acquisition and after 80 to 90 days the surviving hatchling fledges. (Kemp, 2001)

Northern ground hornbill males and females both invest heavily in their offspring. Males provide food for females who are walled into nest cavities with eggs during incubation. Both males and females protect and provide food for hatchlings. Fledged juveniles remain with their parents for up to 3 years, although sex can be determined visually at approximately one year of age. An average of one offspring is raised to independence every 9 years and investment per offspring is exceptionally high. (Kemp, 2001)

Lifespan in captivity is 40 years. (Kemp, 2001)

Northern ground hornbills are primarily terrestrial, though they will fly to capture prey or defend territory, and they roost in trees at night, possibly to avoid predation. They are often seen in pairs, though larger groups are encountered. Groups may form due to juveniles remaining in the parental home range for several years after they reach maturity. Juveniles of many hornbill (Bucerotidae) species, including both ground hornbill species (Bucorvidae), have been observed playing with vegetation and engaging in bill-wrestling. This may refine their motor skills for practical application in foraging and object manipulation as adults. (Kemp, 2001)

Groups of a few to up to 20 (rarely) individuals will defend a territory that may be as large as 260 m^2. (Kemp, 2001)

Males and females sing in booming duets (Kemp, 2001). (Kemp, 2001)

Northern ground hornbills are primarily carnivorous. They eat reptiles, including puff adders (Bitis), cobras (Naja), tortoises (Testudinidae), and lizards, and mammals such as hares (Lepus) and mongooses (Herpestes). Arthropods, mainly insects and arachnids, make up most of their animal diet. They sometimes takes carrion to supplement live prey. Northern ground hornbills follow ungulate herds and forest fires to feed on prey items fleeing these disturbances. Individuals walk up to 11 km per day, overtaking and consuming edible animals in their path. They also dig for arthropods and honeycomb, and rarely consume plant matter. The strong beak is used to grab prey and disarm it. (Kemp, 2001)

Predators of this species include large carnivores, such as leopards. Human predation for food is common in some places, such as northern Cameroon and Burkina Faso. Eggs and nestlings may be preyed on by smaller, terrestrial predators. (Thiollay, 2001; Thiollay, 2006)

Bucorvus abyssinicus is a host for the mallophagan parasites Bucorvellus docophorus, Bucerophagus productus, and Bucerophagus africanus. It also hosts the nematode species Histiocephalus bucorvi and the cestodes Chapmania unilateralis, Idiogenes bucorvi, Ophryocotyloides pinguis, and Paruterina daouensis. A captive, wild-caught individual perished from Aeromonas hydrophila, a common fish pathogen that was previously not known to affect wild populations. This species has also been known to perish in captivity in North America from West Nile Virus. (Canaris and Gardner, 2003; Clay, 1955; Elbel, 1967; Gretillat, 1967; Komar, 2003; Ocholi, RA and Kalejaiye, 1990)

Bucorvus abyssinicus is not often sold or hunted commercially, although they are commonly held in zoos. The species has cultural value in some areas, where hunters may tie the severed head and neck to their own to facilitate stalking of ungulates. The call is often imitated and some villages have entire songs about the male and female duets. (Kemp, 2001)

In some areas northern ground hornbills are killed for breaking windows (by attacking their reflection) and for being cultural symbols of bad luck. (Kemp, 2001)

Bucorvus abyssinicus is not currently threatened, but destruction of suitable nesting trees could impact the species negatively in the future. Disturbed grassland areas are actually preferred for hunting, and therefore it is unlikely that mild to moderate disturbance would have a negative impact on the population. However, where they are hunted for food, such as in northern Cameroon and Burkina Faso, they can be severely depleted or locally extirpated. (Kemp, 2001; Thiollay, 2001; Thiollay, 2006)