Southern Ground Hornbill (Bucorvus leadbeateri) Fact Sheet: Behavior & Ecology

Diurnal (Kemp and Kemp 1980)

• Active in daylight

Daily activity patterns (from Kemp and Kemp 1980)

• Roost in trees at night
• No fixed roost sites; take rest in trees where daylight activities end
• Group members sleep in the same tree or spread between several neighboring trees
• Perch on the distal tips of branches
• Head sunk between the shoulders, bill pointing upwards
• Become active near dawn
• Group members produce deep, booming territorial calls (see description of vocalization below)
• Fly down from trees before sunrise to forage
• c. 30 minutes prior to sunrise
• Forage on the ground
• Time in forage dependent on weather conditions
• Forage nearly all day in cool weather
• Rest for long periods in the heat
• Typically near mid-day
• As long as 6 hours; 09:00-16:00
• Take up roost before sunset

Activity budget (from Kemp and Kemp 1980)

• Spend most active time walking
• Typically 70% of daytime activity; range 38-98%
• Individuals spend more time at rest when temperatures are high
• Play is most common when food is plentiful

Daily travel (Kemp and Kemp 1980)

• Rate of travel slow when walking
• 0.24-0.78 km/hr (0.15-0.48 mi/hr)
• Walk to cover c. 1 km/day

Territory use (from Kemp and Kemp 1980)

• Forage across territorial range
• Do not localize near the nest outside of breeding
• No records of territorial scouting
• Mount defense against trespassers when encountered on daily foraging trips

Home range size (from Kemp and Kemp 1980)

• Occupy large territorial ranges
• c. 100 km² (62 mi²)
• Neighboring nests
• Nearest neighbor c. 9 km (5.6 mi), one study in Kruger National Park, South Africa (Kemp and Kemp 1980)
• Closer, 3.5-4.4 km, in Matobo National Park, Zimbabwe (Witteveen et al. 2013)

Group composition (from Kemp and Kemp 1980)

• A dominant adult male and female pair and their offspring
• 1-2 additional (related) adult males or females may be included in a group
• These individuals do not reproduce
• Lone individuals are most commonly female

Group size

• Range: 2-11 (Kemp et al. 1989)
• 3-5 individuals most common (Kemp and Kemp 1980; Kemp et al. 1989)

Social dynamics (Kemp and Kemp 1980)

• Dominant male and female
• Sole reproductive pair within the group
• Display dominance with threat behaviors and through refusal of food offerings

Advertise to maintain territory

• Produce deep, booming calls
• Call each morning prior to forage (Kemp and Kemp 1980)
• Advertise by calling, while walking or in flight (Kemp 1988)

Cooperative territorial defense (from Kemp and Kemp 1975; Kemp and Kemp 1980)

• Trespassers are pursued in flight
• Commonly followed for long distances when run out of another’s territory
• Up to 3 km (1.9 mi)
• Chases termination
• End with opposing groups calling to one another across the recognized territorial boundary

Aggression

• Agonistic displays (from Kemp and Kemp 1980)
  • Threat displays
    • Raise bill to expose the naked throat skin; head extended
      • Held as high as 70° above the horizontal
      • As intensity increases, the bill is lowered and opened as the aggressor advances at the opponent
    • Bill-beating
      • Peck bill against hard, solid objects producing loud sounds
        • Often occurs when groups meet at a territorial boundary
    • Jerk wings open to flash the white primary feathers of the wings
      • Often accompanies bill-beating
  • Bill grapple
    • Opponents lock bills while twisting the head and pushing against one another

Affiliative behaviors

• Allopreen (mutual preening) (from Kemp and Kemp 1980)
  • Often a prelude to copulation
• Give and receive food (from Kemp 1988; Kemp and Kemp 1980)
  • Interactions likely help define or reinforce social status
    • Food refusal is more common by dominant individuals
  • Participants
    • Food exchanged between nearly all members of a group
      • Most commonly occurs between the dominant male and the dominant female
      • Immature individuals given food by other group members
  • Soliciting food
    • Petitioner approaches potential provisioner with head held down and bill up-tilted
      • Often accompanied by the begging call
      • Crouch the body, quiver the wings, and fluff the feathers of the head and neck
      • May snatch food from provisioner
        • Food carrier may refuse petitioner, giving a head-up threat
        • Carrier often chases the petitioner, attempting to bite it in such situations

Play (from Kemp and Kemp 1975; Kemp and Kemp 1980)

• Extremely playful
  • Mock fight
    • Bill grapple
    • Tug on one another’s feet
  • Chase after and jump on top of one another
  • Compete in ‘Tug of war’ battles for sticks
  • Toss objects with the bill
• Participants
  • Lone play common
  • Immatures commonly play with one another
  • Adults often pestered by young and engage in mock fights

Cooling behaviors (from Kemp and Kemp 1980 unless otherwise noted)

• Hold wings above the body; bill agape (Kemp and Kemp 1975; Kemp and Kemp 1980)
• Forming an umbrella (Kemp and Kemp 1975; Kemp and Kemp 1980)
• Under wing lacks covert feathers
• Face into any available breeze
• Move into shade in extreme heat

Sunbath (from Kemp and Kemp 1980)

• Lay the body down on the ground with wings outstretched
• Tail fanned; head lolls to one side
• One member of a group often walks among basking birds and preens them
• Duration typically brief
• <2 minutes
• Often end bathing with vigorous preening and head scratching

Preen (from Kemp and Kemp 1980)

• Bill nibbles through and cleans feathers
• Also removes thorns from the feet

Scratch and stretch (from Kemp and Kemp 1980 unless otherwise noted)

• Scrape the head with the feet and wrist (Kemp and Kemp 1975, Kemp and Kemp 1980)
• Wipe bill against objects to clean
• Wings extended individually or together
• Leg stretch may accompany stretching of the wing
• Jaw stretch
• Stretch jaw less frequently compared to other hornbill species

Foliage and dust bath (from Kemp and Kemp 1980)

• Rub and fluff feathers in wet leaves or dust

Vocalization

• Principal call (from Kemp 1988 unless otherwise noted)
• Deep, booming territorial call (Coetzee et al. 2014)
• Sound characteristics
• Call composition
• Four notes; ‘hoo hoo hoo-hoo’ or ‘uuh uuh uuh-uuh’
• Three body contractions accompany sound production
• The final contraction produces the double note
• Perception to the human ear
• At a distance, sound appears loud and mellow
• In close proximity, sound appears soft and tinny
• Sound carries over long distances
• Up to 4.5 km (2.8 mi), on a still morning
• Given by group members
• Often by birds at roost just prior to dawn
• Also given while walking or in flight
• Gender-specific variation
• Male call generally much lower than that of female
• An individual may call at either high or low pitch when participating in a duet song
• Click here to hear vocal recordings
• Contact call (from Kemp 1988 unless otherwise noted)
• Low-intensity sound
• Sound characteristics
• 2-3 soft hooting notes
• ‘u-hu-hu’
• Often repeated and leading into a principal booming call
• Sometimes performed in duet
• Given by group members when foraging (Kemp and Kemp 1975)
• Often used to locate one another when not in visual contact (Kemp and Kemp 1975)
• Alarm call (from Kemp 1988)
• Low, grunt-like ‘hu’
• Nasal bray (from Kemp 1988 unless otherwise noted)
• Call of acceptance (Kemp and Kemp 1980)
• Produced when accepting or requesting food
• Given by females and begging immature birds
• Begging immatures call softly for long periods as they walk with other group members
• Call becomes louder as the individual provisioning food approaches more closely
• Head and neck feathers are sometimes raised
• Duet calling
• When foraging (from Seibt and Wickler 1977)
• Enables individuals to infer one another’s location when visual contact is not possible
• Members often forage among tall grasses
• Low call frequencies stand out well against background noise, particularly at ground level
• Continuous calling during forage provides members with repeated positional updates

Terrestrial movements

• Walk (from Kemp and Kemp 1980 unless otherwise noted)
• Stiff, rolling gait
• Stride length: 20-30 cm (8-12 in)
• Only the tips of toes touch the ground
• Do not hop typically (Sclater 1902)
• Run
• When startled (Sclater 1902)

Flight (from Kemp and Kemp 1980 unless otherwise noted)

• Features of flight
• Take flight to bring food to the nest, to cross rivers or dense bush, to move into trees to roost at night, or to chase territorial intruders
• Most often fly within 30 m (c. 98 ft) of the ground
• Rise to over 300 m (984 ft) in pursuit of a territorial trespasser
• Strong, heavy flight (Courtenay-Latimer 1942; Kemp and Kemp 1980)
• Wings beat deeply
• Minimal glide
• Capable of carrying large food masses in the bill
• May produce vocal calls when in the air
• Flight distance
• Cover distances of 2 km (1.2 mi), not uncommon
• Extended, up to 5 km (3.1 mi), in pursuit of a territorial trespasser

Predators

• General predators
• Leopards and Martial Eagle
• Suspected of preying on adults and chicks (Kemp 1988; Kemp 1995)
• Chick-specific predators
• Genet and snakes (Kemp 1995)

Symbiotic relationships

• Parasitic interactions
• Obligate host to a genus of mallophagan feather-lice, Bucorvellus (Kemp 1995)
• Unique species of feather-louse found only on Bucorvus (the Ground Hornbills)
• Mutualistic interactions
• Hornbills glean ticks from warthogs (from Coetzee 2010)
• Warthogs appear to solicit and to yield to grooming; gently drop to the ground when being cleaned
• Hornbills stand next to the warthog while removing and eating ectoparasites

Kleptoparasitism (from Kemp and Kemp 1980)

• Large raptors steal food
• Hornbills are particularly vulnerable when carrying food in their bills
• Raptor flies down at the hornbill; taking food from its bill while in the air

Feeding associations

• Larger herding ungulates and other mammals (from Mlingwa 1989)
• Ground Hornbills walk amongst herd members to feed on the flushed out insects
• Ungulate associations
• Plains zebra (Equus burchelli), warthog (Phacochoerus africanus), giraffe (Giraffa camelopardalis), wildebeest (Connochaetus taurinus), impala (Aepyceros melampus)
• Other mammal associations
• Yellow baboon (Papio cynocephalus)
• Carmine Bee-Eater (Merops nubicoides) (from Fraser 1982; Kemp and Kemp 1980)
• Possible association
• May steal food from the Ground Hornbill
• Reports of the species following groups of Ground Hornbills

In the wild juveniles, such as the one pictured above, live within family units. Families begin each day at a roost site and call loudly to advertise their territory before taking flight to find food. The sounds produced may carry up to 4.5 km (2.8 mi). A group consists of a dominant adult male and female pair and their offspring. Only the dominant (monogamous) pair breeds, but all members aid in providing food for the mother and chicks.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

Coetzee (2010)
Coetzee et al. (2014)
Courtenay-Latimer (1942)
Fraser (1982)
Kemp (1988)
Kemp (1995)
Kemp and Kemp (1975)
Kemp and Kemp (1980)
Kemp et al. (1989)
Mlingwa (1989)
Sclater (1902)
Seibt and Wickler (1977)
Witteveen et al. (2013)