Black Harrier
Circus maurus
Status: Endangered
Range:endemic to Namibia, South Africa
Area of occupancy:23,024 km2
Population estimate in Namibia:<50 birds, 5 prs
Population trend:Fluctuating
Habitat:Desert floodplains, karooid scrub
Threats:No known threats in Namibia

Distribution and abundance


Click to see distribution map

This species is endemic to southern Africa, with the centres of distribution in the W Cape and to a lesser extent the Eastern Cape and Free State Provinces of South Africa (van der Merwe 1981, Simmons 1997). The world population is estimated at less than 1000 birds (Siegfried 1992). Most of this population occurs in the coastal (strandveld) areas of the Cape, with other breeding birds found in the mountains and the higher grassland areas of the E Cape and Free State (Simmons 1997, Curtis et al. 2004). They extend into KwaZulu-Natal north of the Drakensberg and there are scattered records of residents in the n Cape and seasonal (winter) incursions into the southern Kalahari and central Namibia (Simmons 1997). It reaches farthest north on Namibia's cool desert coast around the ephemeral Haonib floodplain and Uniab delta (S Braine, pers obs). The most northerly confirmed nest sites are 28.5oS near Royal Natal NP in e SA (Van Jaarsveld 1986) and near Kleinsee at 29oS (Simmons et al. 2002). There are six sightings from Botswana, as far n as Lake Ngami (Penry 1994). It has the most restricted distribution of any continental harrier species (Simmons & Simmons 2000), estimated at just over 400 000 km2 (Barnes 2000) and recalculated from SABAP data in Simmons (1997) as 386 750 km2 (Jarvis et al. 2001).

The world population has been estimated at about 500 prs (van der Merwe 1981, Siegfried 1992). It is expected to breed in low numbers (maximum 5 prs) in Namibia given frequent sightings of immature birds (S Braine pers obs) in the Hoanib and Uniab River deltas, although this has yet to be confirmed. Densities in coastal South African regions are higher than anywhere else and its low population number are probably the result of the modification of previously common lowland renosterveld for agriculture in the Overberg (Curtis et al. 2004). Because of its reliance on mice which appear to fluctuate with rainfall, harrier populations are expected to fluctuate over time. This may explain the changes reported during the 20th century when it was variously described as going extinct or numerous (van der Merwe 1981, Steyn 1982). They are irruptive in the grasslands of the Free State (B. Colahan pers comm), and the Succulent Karoo plains of the n Cape with years of abundance followed by a complete lack of breeding birds the following year (Simmons et al. 2002).

Ecology

Prefers coastal areas in Namibia especially the Salicornia-like vegetation in the floodplains of the Hoanib and Uniab Rivers, where temperatures are relatively cool, and small mammal populations sometimes abundant (S Braine, J Paterson pers obs). In W Cape mostly found in fynbos vegetation especially coastal thicket and mountain fynbos and less often in the lowland renosterveld and dry restios between these habitats (Simmons et al. 1998, Curtis et al. 2004). In other areas it is found over dry grasslands, road verges, Karoo scrub and wheat fields (van der Merwe 1981, Steyn 1982).

Forages between 1-3 m high over many types of fynbos and grassland vegetation, especially coastal and mountain fynbos, and less often grain fields and other modified habitats. They specialise on hunting mice by slow quartering and a lightning strike into short vegetation or small birds caught after a short chase (Steyn 1982). From records of 138 prey being brought to nests in the Cape Province the diet comprises mainly mice (72%), birds (25%) and reptiles (3%). These proportions vary with habitat with montane harriers taking more bird prey (51% of 47 prey items), than coastal birds which take predominanly mice (87%) (Simmons et al. 2002). Diet in Namibia is unknown.

Egg laying peaks in August-September in South Africa (van der Merwe 1981, Curtis et al. 2004) and they breed at higher densities than casual observations suggest (10 pr/ 0.7 km2 in the W Cape, Simmons et al. 1998, Curtis et al. 2001). There are no breeding records for this species from Namibia (Jarvis et al. 2001), but sightings of immature birds in the Hoanib and Uniab River flooplains suggest breeding has occurred in both areas (S. Braine pers obs).

Breeding success at 1.6-2.5 fledglings/pr (Curtis et al. 2004) in South Africa is higher than that of the African Marsh Harrier (1.1-1.6 fledglings/pr: Tarboton & Allan 1984, Simmons & Simmons 2000), with their ground nests less likely to fail due to predation.

Threats

There are few known threats to this species in Namibia. The small population which migrates northwards from South Africa covers a wide variety of karooid habitat which may be overgrazed especially in s Namibia. The resident population in the nw floodplains occur within the Skeleton Coast NP and is thus protected from cattle grazing and fire.

In South Africa fragmentation of lowland habitat is the main worry but most of the birds found breeding occur in protected areas such as the West Coast NP or private reserves (Curtis et al. 2004). Foraging over wheatfields which is rare, may expose birds to herbicides and pesticides as in African Marsh Harriers Circus ranivorus (de Kock & Simmons 1988) and this may explain the high incidence of unhatched eggs (18%) and a number of dead adults found in South Africa (Simmons et al. 2005).

The intense grazing pressure in s Namibia may isolate the birds found in the northern regions from the core South African population but this may have little direct impact on a migratory species such as this.

Conservation status

This species is classified as Endangered because of its very small population of less than 50 birds in Namibia, and only about 5 suspected breeding prs. There is no indication of decline but like South African populations it fluctuates in Namibia with many birds in some years and few in others. It is suspected that this is associated with fluctuations in small mammal populations on which it feeds (Simmons et al. 2005).

It is only classified as Near-Threatened in South Africa (Barnes 2000) even though it is now classified in a higher category (Vulnerable) in global assessments (Birdlife International 2004). This classification was based on the assumption that it is heavily reliant on private farmland (in South Africa) making it susceptible to land-use change. Present day, most populations occur in coastal areas, mainly protected areas, while many others occur in mountains not under agriculture. The intervening lowlands, which once comprised renosterveld have been largely transformed to wheatlands decades ago, a habitat in which these birds now rarely breed (Curtis et al. 2004). Birds do indeed forage over these areas but most foraging occurs within renosterveld (O Curtis 2005). If renosterveld or core breeding habitat is further fragmented through agriculture, birds may be forced to forage over transformed habitat and breeding sites and population size may be further eroded. In Namibia possible breeding birds are protected within the Skeleton Coast Park.

Actions

Monitoring of populations in Namibia's north-western rivers is a priority, especially to confirm that breeding occurs (likely October-November). This is best done when small mammals are abundant and the presence of birds should then be checked in other coastal rivers where extensive Salicornia thickets are present. The wetter areas may then hold breeding birds. The distribution of birds that migrate in winter to central Namibia is poorly known, but the winter habitat may be crucial to the well-being of the W Cape core population. Thus understanding the habitat needs of wintering birds and protecting the grasslands or shrublands of the Nama Karoo may prove to be an important conservation action. Most attention however is required in South Africa to safeguard the core populations.

From: Simmons RE & Brown CJ 2006. Birds to watch in Namibia: red, rare and endemic species. National Biodiversity Programme, Windhoek, Namibia

References

Barnes KN (ed) 2000. The Eskom Red data book of birds of South Africa, Lesotho and Swaziland. Birdlife South Africa, Johannesburg.

Birdlife International 2004 Threatened Birds of the World. CD-ROM Birdlife International, Cambridge.

Braine, Steve unpublished data. Naturalist, (hobatere@mweb.com.na)

Colahan, Brian personal communication Ornithologist, Free State Province (colahan@dteea.fs.gov.za)

Curtis O 2005 Responses of raptors to habitat fragmentation: from individual responses to population susceptibility Masters thesis, University of Cape Town

Curtis O, Jenkins A, Simmons R 2001 The Black Harrier - work in progress. Africa: Birds & Birding 6: 30-36.

Curtis OE, Simmons RE, Jenkins AR 2004 Black Harrier Circus maurus of the Fynbos Biome, South Africa: a threatened specialist or an adaptable survivor? Bird Conservation International 14:233-245.

De Kock AC, Simmons R 1988 Chlorinated hydrocarbon residues in African Marsh Harrier eggs and concurrent reproductive trends. Ostrich 59:180-181

Jarvis A, Robertson AJ, Brown CJ, Simmons RE 2001. Namibian Avifaunal Database. National Biodiversity Programme, Ministry of Environment & Tourism, Windhoek.

Paterson, John personal observation, nature conservator, Skeleton Coast Park (john@paterson.alt.na)

Penry H 1994 Bird atlas of Botswana. University of Natal Press, Pietermaritzburg Siegfried WR 1992 Conservation status of the South African endemic avifauna. S. Afr. J. Wildl Res 22:61-64

Simmons RE 1997 Black Harrier Circus maurus. In: Harrison JA, Allan DG, Underhill LG, Herremans M, Tree AJ, Parker V, Brown CJ (eds). The Atlas of Southern African Birds. Vol 1: 241-243. BirdLife South Africa, Johannesburg.

Simmons RE, Simmons JR 2000 Harriers of the World: their behaviour and ecology. Oxford University Press, Oxford.

Simmons RE, Curtis O, Jenkins AR 1998 Black Harrier conservation and ecology: preliminary findings 2000. J. African Raptor Biology 13:33-38

Simmons R, Curtis O, Jenkins AR 2002. Third annual report of the Black Harrier Project. Unpublished Report, FitzPatrick Institute, University of Cape Town.

Simmons RE, Curtis O, Jenkins AR 2005 Black Harrier Circus maurus In: Hockey PAR, Dean WRJ, Ryan P (eds) Roberts Birds of Southern Africa VII. Pp 502-503 Black Eagle Publishing, Cape Town.

Steyn P 1982 Birds of Prey of Southern Africa. David Philip, Cape Town.

Van der Merwe F 1981 Review of the status and biology of the Black Harrier. Ostrich 52:193-207

Van Jaarsveld J 1986 Black Harrier breeding near Royal Natal Park, RSA. Gabar 1: 27

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