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Secretary Bird (Sagittarius serpentarius) Fact Sheet: Behavior & Ecology

Activity Cycle

  • Diurnal
  • Not active until well after sunrise. Spend time preening and warming in the sun.
  • Mated pairs travel together throughout the day in the same vicinity but hunt independently.
  • Activity is centered around the roosting or nesting tree.
  • May pause to roost during the heat of the day, often in the nesting tree.
  • Foraging occurs again in the afternoon, and pairs return an hour or two before dark.
  • Can cover 2 - 3 km per hour, and can roam 20 – 30 km a day.
  • Take breaks to preen, rest, dust bathe, and drink.
  • Return to roost in late afternoon or dusk, with head tucked under wing.
  • Pant to keep cool when exposed to high temperatures.

Territory Size

  • Usually sedentary, but nomadic when prey fluctuates.
  • Mated pairs occupy 20 sq km of territory in Kruger National Park, 100 to 230 sq km in the Transvaal.
  • Pairs can have territories over 20 sq km in mixed tree and grass areas, 45 sq km in dry grassland, 70 sq km in montane grassland within South Africa.
  • Densities of 50 sq km per pair have been reported for parts of the Transvaal and Zimbabwe, but may become as low as 100-500 sq km during years of low rainfall, or in more arid parts of the continent.

Territorial Behavior

  • Pairs defend against encroaching Secretaries by chasing and jumping over them, striking downwards with their feet and uttering deep croaking calls.
  • Invading Secretaries usually run away when confronted with an attack.
  • When the victor returns to its partner, runs circles around it with crest feathers lifted.
  • No aggression observed between siblings.

Communication

Displays

  • Pendulum displays are used during courtship and mating, and may be performed by one or both members of a pair.
    • Displays may last as long as 15 minutes, stalling and then swooping down with wings closed, then swinging up again and repeating the performance. Pairs may also swoop at each other, rolling over to present the feet, even when one bird is on the ground near the nest.
    • At the peak of each pendulum flight, bird closes wings briefly, then flicks them open before turning downward, producing a flash of silver-grey as underwing coverts appear beneath black wing feathers.
  • Mating displays can occur up to six months before egg-laying.
  • Bowing or greeting displays are used by mates when exchanging brooding duties.
    • Sitting parent stands and raises and lowers the head, similar to the "up-down" display of many storks. May include the croaking call, fanning the tail almost vertically above the back, exposing the white undertail coverts at each bow.
    • Bowing displays most common during nest-building and early stages of incubation.

Vocalizations

  • Generally silent, except when announcing their presence.
  • Call is a deep guttural croak that becomes a loud roaring groan at high intensity, sometimes uttered with the head thrown back.May be cried:
    • In flight during pendulum displays
    • On the ground during fights
    • At the nest by mates during bowing or greeting displays
    • By large chicks in response to predators
  • A single high croak indicates alarm. Deeper croaks are used to threaten.
  • Soft clucking calls and low whistles may be given by mates at the nest.
  • Small chicks beg with soft cheeping calls that become insistent clucking, mewing, squealing and then braying notes. As the birds become older and hungrier, calling can even continue at night.

 

Locomotion

On the ground

  • Sometimes pairs run over grassland with wings held above the back, possibly in pursuit of large snakes or other prey, but may be a form of display.
  • May stride quickly, looking from side to side, or shuffles slowly looking for prey.
    • 120 paces / minute
    • 16 inch stride
    • 2 mi / hr

Flight

  • Capable fliers, can execute impressive acrobatic displays at considerable height.
  • Sighted at over 3,658 m (12,000 feet) elevation.
  • Commonly soar on thermals for travel and perform undulating nuptial display flights.

Dispersal & Migration

  • Secretaries are sedentary during breeding season and as long as food is available.
  • Nomadic in most areas in response to changes in rainfall, grazing and fires.
  • Adult males are usually the last to abandon territories, while juveniles wander widely in search of areas unoccupied by mated pairs.
  • Birds may enter and breed regularly in an area for several years and then be absent or only present in greatly reduced numbers.

Interspecies Interactions

  •  Aggressively fly against intruding raptors and birds competing for food and territory.

Secretary Bird

Secretary bird head

Image credit: © San Diego Zoo Global. All rights reserved.

Page Citations

Brown (1972)
Kemp (1994, 1995)
Steyn (1982)
Tarboton (1990)

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