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Tyto capensisAfrican grass-owl(Also: grass owl)

By Jenny McKinney

Geographic Range

African grass owls (Tyto capensis) range through the wetlands of sub-equatorial Africa and are also found in the high altitudes of the Cameroon Mountains. (Reigert, et al., 2007)

Habitat

African grass owls are most commonly observed near bodies of water, such as creeks, ponds, or marshes. Unlike most predatory birds, they roost on the ground among the tall grass that grows in the wetlands. They trample the grass into a domed platform to create a nesting or roosting area and create tunnels or runways through the grass to connect multiple roosts together. (Brown, et al., 2009; Konig, et al., 2010)

  • Range elevation
    0 to 3200 m
    0.00 to 10498.69 ft

Physical Description

As chicks, African grass owls have white downy plumage, which is replaced at 18 days with a second set of feathers that are dense and pale brown or buff in color. The facial disk is brown and pales towards the outer edges. Juveniles remain unspotted and dark on top with deep golden feathers below and often still look downy. As adults, they are medium-sized owls, measuring 38 to 42 cm from tail to tip. Adults feature a heart-shaped facial disc that is white in color and outlined in yellow with dark colored spots. They have dark brown or black eyes and pale pink or white beaks. The upper parts of their bodies are dark brown, while the underparts are white. Their long white-feathered legs are an adaptation to their habit of walking and nesting on the ground. The toes of African grass owls are bristled. Females appear to be larger than males but males and females are similar in appearance. (Ansara-Ross, et al., 2009; Burton, 1973; Konig, et al., 2010; Redman, et al., 2009)

  • Sexual Dimorphism
  • female larger
  • Range mass
    355 to 520 g
    12.51 to 18.33 oz
  • Range length
    380 to 420 mm
    14.96 to 16.54 in
  • Range wingspan
    283 to 345 mm
    11.14 to 13.58 in

Reproduction

African grass owls are monogamous. It is unknown how mates are found and attracted due to the secretive nature of these owls. However, during incubation, males care for and feed females. Males and females defend the nest and communicate with each other when bringing in prey to the chicks. (Crafford and Ferguson, 1999)

African grass owls generally breed between December and August. Food supply determines where birds choose to nest. Females lays 2 to 4 eggs, which are white and approximately 41 by 32 mm in size. (Brown, et al., 2009; Burton, 1973; Konig, et al., 2010)

  • Breeding interval
    African grass owls breed yearly, usually in the spring.
  • Breeding season
    African grass owls breed from December to August.
  • Range eggs per season
    2 to 4
  • Range time to hatching
    32 to 42 days
  • Range fledging age
    5 to 7 weeks
  • Average time to independence
    10 weeks
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Both female and male African grass owls provide parental investment in the development of the young. Females incubate the eggs for 32 to 42 days. Males bring females food during incubation. For the first 10 days, females continue to stay with the chicks. Males continues to forage for food for the family. At 5 weeks old, the chicks start to become mobile. At 7 weeks old, the chicks start to learn to fly. The chicks remain with their parents until 10 weeks old. (Burton, 1973; Konig, et al., 2010)

  • Parental Investment
  • male parental care
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female

Lifespan/Longevity

It is thought that African grass owls have similar lifespans to their cousins, barn owls (Tyto alba). Barn owls live between 1 and 5 years in the wild and between 20 and 25 years in captivity. Research is limited in this area due to the secretive and nocturnal behavior of African grass owls. (Burton, 1973; Konig, et al., 2010)

Behavior

African grass owls are primarily nocturnal. Depending on the availability of food, these owls may hunt in the early evening or early morning. They don't build a nest as other birds do. Instead, they stomp the grass down, creating a pad of trampled grass to use as a roost. They nest in pairs or small parties, connecting the roosts together by tunneling through the grass. (BirdLife International, 2012; Burton, 1973; Konig, et al., 2010)

Home Range

African grass owls are found most commonly in areas of tall grass and near bodies of water. They move roosting areas if there is a shortage of food, but prefer to stay in one place. Their home ranges are thought to be extremely large, but have not been measured in recent years. (Ansara-Ross, et al., 2009; BirdLife International, 2012; Burton, 1973; Redman, et al., 2009)

Communication and Perception

African grass owls use sight, sound, and touch to navigate at night. They produce sharp, double-clicking calls and long phrases of single clicking noises. These calls often occur during flight and are observed during social communication among individuals. The clicking calls also assist these birds in hunting and navigating effectively in their habitat. (Crafford and Ferguson, 1999)

Food Habits

African grass owls prefer to eat small rodents, such as shrews or African vlei rats (Otoyms). Most prey comes from close to the ground, but African grass owls are also known to capture bats, large insects, and small birds in the air. (Baxter and Matshili, 2009; Konig, et al., 2010; Reigert, et al., 2007)

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • birds
  • mammals
  • insects

Predation

African grass owls use a clicking call to communicate with each other. Nesting on the ground makes it common for a nest to be destroyed, but specific reports of predation are not found in the literature. Humans, and their impact on African grass owl habitat, seem to be the most prominent threat to this species. (Ansara-Ross, et al., 2013; BirdLife International, 2012; Crafford and Ferguson, 1999)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

African grass owls are important predators of small mammals in their habitat. They play a role in managing populations of small rodents in sub-Saharan Africa. (Ansara-Ross, et al., 2013; Reigert, et al., 2007)

Economic Importance for Humans: Positive

Humans and African grass owls rarely have any contact. Their nocturnal habits make it difficult for observations to be completed. Humans benefit from the declining population of the species indirectly. Festivals are thrown for African grass owls to celebrate and bring recognition to their declining populations. There are many groups that are working closely with the government to conduct research and educate people about African grass owls.

  • Positive Impacts
  • ecotourism
  • research and education

Economic Importance for Humans: Negative

There are no known adverse effects of African grass owls on humans.

Conservation Status

African grass owls have experienced rapid population declines due to human-induced habitat changes as the result of industrialization and urbanization. Population size hasn't been quantified, but populations of these owls are considered vulnerable. (BirdLife International, 2012)

Contributors

Jenny McKinney (author), University of Wyoming, Hayley Lanier (editor), University of Wyoming - Casper, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

marsh

marshes are wetland areas often dominated by grasses and reeds.

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

References

Ansara-Ross, T., M. Ross, V. Wepener. 2013. The use of feathers in monitoring bioaccumulation of metals and metalloids in the South African endangered African grass-owl. Ecotoxicology, 22: 1072-1083.

Ansara-Ross, T., V. Wepener, G. Verdoorn, M. Ross. 2009. Sexual dimorphism of four owl species in South Africa. Ostrich: Journal of African Ornithology, 79: 83-86. Accessed November 04, 2013 at http://dx.doi.org/10.2989/OSTRICH.2008.79.1.11.366.

Baxter, R., A. Matshili. 2009. An analysis of Barn and Grass Owl pellets from Alice, Eastern Cape, South Africa. Ostrich: Journal of African Ornithology, 74: 233-235. Accessed November 04, 2013 at http://dx.doi.org/10.2989/00306520309485400.

BirdLife International, 2012. "Tyto capensis" (On-line). IUCN Red List of Threatened Species. Accessed November 04, 2013 at http://www.iucnredlist.org.

Brown, M., M. Perrin, B. Hoffman. 2009. Reintroduction of captive-bred African Grass-Owls Tyto capensis into the natural habitat. Ostrich: Journal of African Ornithology, 78: 75-79. Accessed November 04, 2013 at http://dx.doi.org/10.2989/OSTRICH.2007.78.1.11.55.

Burton, J. 1973. Owls of the World their evolution, structure, and ecology. New York: E.P.Dutton & Co, INC..

Crafford, D., J. Ferguson. 1999. Why do grass owls (Tyto capensis) produce clicking calls?. Journal of Raptor Research, 33: 134-142.

Konig, C., F. Weick, J. Becking. 2010. Owls of the World their evolution, structure, and ecology. Huntingdon, GBR: A & C Black.

Redman, N., T. Stevenson, J. Fanshawe. 2009. Birds of the Horn of Africa. London: GBR: A&C.

Reigert, J., O. Sedlacek, R. Hutterer. 2007. Diet of sympatric African grass owl (Tyto capensis) and spotted eagle owl (Bubo africanus) in the Bamenda Highlands, NW Cameroon. Journal of African Ecology, 46: 428-431.

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