Black Harrier (Circus maurus)

[order] ACCIPITRIFORMES | [family] Accipitridae | [latin] Circus maurus | [authority] Temminck, 1828 | [UK] Black Harrier | [FR] Busard maure | [DE] Mohrenweihe | [ES] Aguilucho negreo | [NL] Zwarte Kiekendief

Medium-sized harrier. Adult striking, with black plumage plus boldly striped black-and-white tail, white rump and yellow legs, eye and cere. White undersides to primaries and secondaries give huge white wing panels, contrasting with black coverts and body. Immature dark brown and heavily mottled and streaked, but has obvious white rump and banded tail. Juvenile and immature much darker and more blotched on underparts than the warm brown streaking of similar-age Pallid Harrier C. macrourus and Montagu’s Harrier C. pygargus; which also have large white underwing panels.

Africa : South. Circus maurus is restricted to southern Africa, where it is concentrated in the Western Cape (its core range), and occurs in the Eastern Cape, the Northern Cape and Free State (where it is irruptive in both areas), in South Africa, and is also found in Botswana and Lesotho (non-breeding birds), with a tiny isolated population in northern Namibia (less than 50 birds including about five pairs).

It is a cool, dry-country species, frequenting coastal and montane fynbos, highland grasslands, Karoo subdesert scrub, open plains with low shrubs and croplands. It often breeds close to coastal and upland marshes with tall shrubs or reeds, occurring in dry steppe and grassland areas further north in the non-breeding season. In the western cape of South Africa it is most abundant in coastal and montane fynbos, whilst in Namibia it favours coastal river floodplains. Damp sites, near vleis, marshes or streams, are preferred for breeding, while south-facing slopes are preferred in montane areas.

Nests are built on the ground and usually hold two to five eggs which are incubated for a little over a month. In south-western South Africa, egg-laying takes place in June-November, with peaks in July and September. The may nest in loose colonies of 3-4 pairs, 50 meter apart. Nest is a messy pad of grass based on stems, reeds and/or weeds. YOung fledge after about five to six weeks.

It prefers open ground with low vegetation for hunting, where it feeds on a diet comprising mainly of small mammals, especially Otomys and Rhabdomys species. Whilst mammals make up the vast majority of prey taken at coastal sites, with reptiles and birds also taken, birds make up a slightly greater proportion than mammals in the diet of pairs nesting in montane habitats. Local fluctuations in breeding numbers may be related to population cycles in its prey base, such as mice whose numbers fluctuate with rainfall, especially in the more arid regions.

httpv://www.youtube.com/watch?v=xpgJsEY7Gvo

copyright: Francesc Capdevila i Torrell

This species is classified as Vulnerable, despite its huge range, because it has a very small population. This and its virtual disappearance from agricultural lowlands make it highly reliant on protected areas in its core breeding range.
The species has conceivably lost 50 % of its preferred breeding habitat over the last century, and present rates in the Overberg may be over 1% per annum. Habitat is primarily lost to agriculture, and this is compounded by the uncontrolled burning of fynbos and grassland, which renders these habitats unsuitable for breeding for about five years. Alien vegetation and urbanisation are also cited as causes of habitat loss. In south-western South Africa, it is thought that breeding birds have been displaced from prime lowland habitats (renosterveld and fynbos) by the spread of cereal agriculture, with breeding pairs presently occupying only coastal areas, with high productivity, and montane habitats, where breeding success is low and levels of nest predation are high. Rodent populations in areas of wheat cultivation may be as low as 33% of those found in renosterveld vegetation, and remnant patches of renosterveld, which continue to be degraded, hold lower numbers of rodents than coastal strandveld vegetation. Low hatching rates, possibly as a result of high pesticide residues, is an increasing threat now that many remaining breeding habitats are surrounded by agricultural areas. The ingestion of herbicides and pesticides may account for the death of some adults in South Africa, while road deaths adjacent to west coast breeding grounds numbered six birds over one breeding season in 27. Drainage, impoundment and inappropriate management of vleis, marshes or streams near breeding grounds could prove detrimental. Climate change in South Africa is predicted to cause a decrease in overall winter rainfall in the core breeding areas, which is likely to lead to a reduction in mouse populations and disruption to breeding. The same threats may apply to the species in Namibia, and the favoured habitats of the migrant population may be overgrazed, particularly in southern Namibia. Overgrazing in southern Namibia is attributed mainly to resident pastoralists and ’emergency grazing’ by farmers from elsewhere, which is offered during years of good rainfall.

Most birds migrate North in winter to dry steppe and grassland areas of South Namibia, South Botswana and South Transvaal.