Black-breasted buzzard (Hamirostra melanosternon)

Black-breasted buzzard fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Black-breasted buzzard description

The majestic black-breasted buzzard (Hamirostra melanosternon) is one of Australia’s largest birds of prey ⁽²⁾. Both sexes are similar in appearance, but the female is generally larger than the male. The black-breasted buzzard has a striking head with a small crest and a long, fairly slender bill with a rounded cere. Powerful, unfeathered legs end in weak, whitish toes ⁽³⁾, while the tail is short and square shaped ⁽⁴⁾.

The adult black-breasted buzzard has a black forecrown, face, breast and upper back. The rest of the back and shoulders are black with reddish-brown flecks, making the almost completely rufous nape, thighs and lower abdomen more conspicuous. Compared to the more rufous shoulders, the wings are browner and have prominent whitish patches on the base of the primary feathers. The black-breasted buzzard’s eyes are brown, and the tail is grey-brown at all ages ⁽³⁾.

Juvenile black-breasted buzzards are distinct in appearance from the adult birds, and are not considered to be fully adult until their fifth year. The immature stages between juvenile and adult are also clearly discernable. The juvenile’s head and underparts are reddish-brown with blackish streaks on the crown, down the back of the neck and on the throat. This streaking extends onto the chest, where it is even more conspicuous. The back is blackish-brown and the shoulders appear more russet due to the wide reddish-brown edgings of the wing-coverts. The black primary feathers have off-white patches at the base, and the secondaries are faintly barred ⁽³⁾.

At two to four years of age, immature black-breasted buzzards are less rufous than the juvenile bird, appearing browner due to the streaks on the breast becoming more extensive and the black areas, such as the forehead and face, becoming darker in the third year. The young bird does not develop a solid black breast until its fourth year. Juvenile and immature black-breasted buzzards have pale hazel eyes until they are at least three years old, at which time they begin to darken ⁽³⁾.

Predominantly a silent bird, even during aerial courtship, the black-breasted buzzard is usually only vocal during interactions with other species. When mobbed by large passerines or smaller raptors, or when attacking other birds, its main distress call is a hoarse ‘yik-yik’ shriek or a long whistled alarm ⁽³⁾.

Size

Wingspan: up to 1.5 m ⁽²⁾

Male weight: 1.15 - 1.24 kg ⁽³⁾

Female weight in captivity: 1.21 - 1.45 kg ⁽³⁾

Black-breasted buzzard biology

The black-breasted buzzard searches for prey mainly while in the air, soaring at medium to low heights across open ground or higher up in woodland treetops. It forages by gliding backwards and forwards across an area, swooping to take prey from the ground or occasionally from trees ^{(3) (4)}. The main prey items of the black-breasted buzzard include mammals such as rabbits and small rodents, as well as birds, lizards and small snakes, some insects, and carrion ⁽³⁾.

As well as being an active hunter, the black-breasted buzzard is also considered to be an egg-eating specialist, displaying unique behaviour that sets this species apart from most other raptors ⁽⁷⁾. Preying on the nestlings and eggs of ground-nesting birds such as the emu (Dromaius novaehollandiae), brolga crane (Grus rubicunda) and Australian bustard (Ardeotis australis), a black-breasted buzzard will drive adult birds off their nests by opening its wings in a threatening manner. It breaks open smaller eggs with its bill, or by dropping them on the ground ⁽³⁾.

If the eggs are too thick, like those of large birds such as the emu, the buzzard will either hurl stones at the eggs from a standing position ^{(3) (4)}, or drop rocks from the air to break the shell ⁽⁸⁾. Young black-breasted buzzards raised away from adults still exhibit this tool use, proving that the specialist behaviour is innate and not learned. However, the young birds do have to first learn to recognise eggs as a potential food source ⁽⁷⁾. The black-breasted buzzard is one of only two raptors to habitually use tools when feeding ⁽⁴⁾. There have also been some reports of co-operative hunting within this species ⁽³⁾.

The black-breasted buzzard breeds throughout its entire range, although it shows a definite preference for some areas. In times of drought it may forego breeding since nesting normally takes place during rainier seasons ⁽⁵⁾, usually occurring from June until November, and peaking between August and October ⁽³⁾. During the breeding season, pairs of black-breasted buzzards soar over their nesting territory for hours at a time, rising and falling in a display and sometimes performing mock attacks, rolling and parrying with each other. This species is monogamous, and pairs nest solitarily ⁽³⁾.

The nest of the black-breasted buzzard is around 70 to 120 centimetres wide and 40 to 55 centimetres deep, and is built from sticks and lined with green leaves ⁽⁴⁾. It is placed approximately 6 to 22 metres off the ground, usually in the fork of a dead or living tree branch ^{(3) (4)}. The clutch size of this species is normally two eggs, but can range between one and three. Incubation is carried out equally by both sexes over a period of approximately 36 to 40 days, and the black-breasted buzzard chicks fledge after 56 to 60 days, after which they remain dependent on the adult birds for around two months ⁽³⁾. Usually only one chick survives and fledges the nest, but occasionally a second chick is also successful ⁽⁴⁾.

Although normally seen alone or in pairs, the black-breasted buzzard may occasionally gather in groups of ten or so individuals at carrion and communal roosts. ⁽³⁾. It flies with a powerful ‘rowing’ action or, when in pursuit, with rapid, shallow wing beats. Its most characteristic locomotive behaviour is its ability to soar effortlessly, gliding steadily ⁽⁴⁾ and rocking side to side as it does so ⁽³⁾. Black-breasted buzzards soar in wide sweeping arcs instead of the tight spiralling that is characteristic of most raptors ⁽⁴⁾. 

Black-breasted buzzard range

The black-breasted buzzard is endemic to Australia ⁽⁵⁾, being found across the majority of the mainland ⁽⁴⁾ and on some offshore islands, such as Barrow Island ⁽⁶⁾. The only areas from which it is absent are those with high rainfall in the south and east ⁽⁴⁾. This species is far more common in central and northern Australia than in the south ^{(3) (5)}.

Although adult black-breasted buzzards are generally sedentary, they may become nomadic in drought conditions ⁽³⁾. 

Black-breasted buzzard habitat

Occupying a wide range of inland habitats, the black-breasted buzzard is often found around wooded watercourses, which are its preferred breeding habitat. This bird of prey hunts mainly in sparsely timbered woodland and grassland ⁽²⁾. It is also present in open sclerophyll forest and eucalyptus woodland, scrub-steppe, dry heathland and open country, including grass plains and sandy desert. The black-breasted buzzard occurs from sea level to elevations of 1,000 metres ⁽³⁾.

Black-breasted buzzard status

The black-breasted buzzard is classified as Least Concern (LC) on the IUCN Red List ⁽¹⁾.

Black-breasted buzzard threats

Although the black-breasted buzzard population appears to be declining, this decline is not currently considered significant enough for the species to be classified as threatened. The species has an extremely large range, despite the habitat degradation that is contributing to its population decline ⁽⁹⁾.

Although not nationally threatened in Australia, the black-breasted buzzard is considered to be vulnerable in New South Wales and rare in South Australia. Populations in the south are declining due to the degradation and clearance of suitable habitat, as well as mammal prey declines and carcass poisoning. The black-breasted buzzard is sensitive to human activity near the nest and is also at risk from being killed while scavenging on the road ⁽⁴⁾. This species also suffers from illegal egg collecting ^{(4) (9)}.

Black-breasted buzzard conservation

No global conservation measures are currently in place for the black-breasted buzzard. However, the Office of Environment and Heritage in New South Wales has outlined a recovery strategy for this species ⁽²⁾. Proposed actions include educating and encouraging landowners to protect and rehabilitate foraging habitat, protecting nesting habitat, and performing surveys of the black-breasted buzzard population. It will also be important to report suspected egg collection or shooting, monitor secondary poisoning from pest control, and study the reproduction of this species at its nest sites ^{(2) (10)}.

Find out more

Find out more about the black-breasted buzzard:

• Office of Environment and Heritage, New South Wales - Black-breasted buzzard:
  http://www.environment.nsw.gov.au/threatenedspeciesapp/profile.aspx?id=10395
• BirdLife Australia - Black-breasted buzzard:
  http://www.birdlife.org.au/bird-profile/black-breasted-buzzard
• BirdLife International - Black-breasted buzzard:
  http://www.birdlife.org/datazone/speciesfactsheet.php?id=3338

More on threatened species in New South Wales, Australia:

• Office of Environment and Heritage, New South Wales:
  http://www.environment.nsw.gov.au/threatenedspecies/index.htm

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Glossary

Carrion

The flesh of a dead animal.

Cere

In birds, an area of skin at the base of the upper mandible of the beak, surrounding the nostrils.

Endemic

A species or taxonomic group that is only found in one particular country or geographic area.

Incubation

The act of incubating eggs; that is, keeping them warm so that development is possible.

Monogamous

Having only one mate during a breeding season, or throughout the breeding life of a pair.

Morph

One of two or more distinct types of a given species, often distinct colour forms, which occur in the same population at the same time (that is, are not geographical or seasonal variations).

Nomadic

A species which roams irregularly from place to place in search of food and water, without returning to a fixed location.

Passerines

A group of more than 5,000 species of small to medium-sized birds, sometimes known as perching birds or song birds, which have widely varied plumage and shape. They all have three toes pointing forward and one pointed backward, which assists with perching.

Primary feathers

The main flight feathers projecting along the outer edge of a bird’s wing.

Raptor

Bird of prey.

Sclerophyll

A type of vegetation with hard, thick-skinned leaves; for example, eucalypts and acacias.

Secondary feathers

The shorter flight feathers projecting along the inner edge of a bird’s wing.

Steppe

A vast grassland plain, characterised by few trees and low rainfall.

Territorial

Describes an animal, a pair of animals or a colony that occupies and defends an area.

Territory

An area occupied and defended by an animal, a pair of animals or a colony.

Wing-coverts

Small feathers which cover the bases of other larger feathers, helping to smooth airflow over the wings.

References

1. IUCN Red List (November, 2012)
   http://www.iucnredlist.org/
2. Office of Environment and Heritage, New South Wales - Black-breasted buzzard (November, 2012)
   http://www.environment.nsw.gov.au/threatenedspeciesapp/profile.aspx?id=10395
3. Christie, D. and Ferguson-Lees, F. (2010) Raptors of the World. A&C Black Publishers, London.
4. Debus, S. (2012) Birds of Prey of Australia: A Field Guide. CSIRO Publishing, Collingwood, Australia.
5. BirdLife Australia - Black-breasted buzzard (November, 2012)
   http://www.birdlife.org.au/bird-profile/black-breasted-buzzard
6. Moro, D. and MacAulay, I. (2010) A Guide to the Birds of Barrow Island. Chevron Australia, Perth. Available at:
   http://www.chevronaustralia.com/environment/protectingenvironment/nature-books.aspx
7. Joseph, L. and Olsen, P. (2011) Stray Feathers: Reflections on the Structure, Behaviour and Evolution of Birds. CSIRO Publishing, Collingwood, Australia.
8. Burton, M. and Burton, R. (2002) International Wildlife Encyclopedia. Third Edition. Marshall Cavendish, New York.
9. BirdLife International - Black-breasted buzzard (November, 2012)
   http://www.birdlife.org/datazone/speciesfactsheet.php?id=3338
10. Office of Environment and Heritage, New South Wales - Priority actions for black-breasted buzzard (November, 2012)
    http://www.environment.nsw.gov.au/threatenedspeciesapp/PasSearchSpecies.aspx?speciesName=Black-breasted+Buzzard&generalType=Birds