Rationale
(Changed due to Genuine (recent))
The decrease in the regional population of African Marsh Harrier Circus ranivorus is believed to be sufficiently rapid to satisfy the thresholds for regionally Endangered under the population trend criterion A2 (greater than 50 % decline over a 24 year period (three generations)). The population size is believed to fulfil the requirements for regionally Endangered under the population size criterion C1 (less than2 500 mature individuals with a continuing decline estimated to be greater than 20% in the next five years or two generations, or with a specified population structure).
Distribution
The African Marsh Harrier is sparsely distributed across wetlands throughout central and east Africa, and southwards to southern Africa (Ferguson-Lees and Christie 2001). It is absent from areas with less than 300 mm of annual rainfall (Simmons 1997). The Okavango Delta in northern Botswana is considered to be a stronghold (Simmons 1997), with the species also occurring in neighbouring Zimbabwe and Mozambique (Ferguson-Lees and Christie 2001). Within the region, it occurs in high densities in higher rainfall coastal regions from Zululand down to Western Cape, as well as in Mpumalanga, Gauteng, Limpopo and North West provinces (Simmons 2005). It is absent from the drier parts of Northern Cape and inland areas parts of Western Cape. In Swaziland, the species is patchily distributed across the Highveld in the west of the country and is a non-breeding visitor to the eastern Lowveld (Parker 1994).
The EoO estimates indicate that the species' overall range has not contracted between the atlas periods, but the AoO estimates show an alarming 46.51% decline at sites within its original range. It is unlikely that short-term fluctuations due to rodent populations and rainfall can explain the decrease in AoO as SABAP2 data gathering has been running for more than five years (RE Simmons pers comm.). In addition, the species is easily identifiable and highly conspicuous when foraging. The African Marsh Harrier is well represented within the Important Bird Area network in the region, although the decrease in AoO outside of these sites is a cause for concern.
Population
The global population has not been quantified (BirdLife International 2014). Cohen (2000) estimated there to be 6 000-10 000 mature individuals in the region. The number of mature individuals present in Swaziland is not known (Monadjem et al. 2003), but is estimated to be less than 100. Tarboton and Allan (1984) estimated that a pair of African Marsh Harriers require a minimum of 100 ha of wetland as a breeding territory. The current regional AoO is approximately 3 000 km2 or 300 000 ha which could, conceivably, hold up to 6 000 mature individuals. The uncertainty as to how many wetlands of greater than 100 ha within the region are occupied, the relative densities at which this species occurs in different habitat types, and the area outside of wetlands that is required for foraging, make estimating a regional population problematic. The rapid decline in AoO indicated by SABAP2 suggests that the 20% decline in the regional population predicted by Cohen (2000) has indeed occurred, and in all likelihood has occurred more rapidly than predicted. It is estimated that the current regional population is 3 500-4 500 mature individuals. The confidence in this regional population estimate is low.
Population trend
The global population is in decline (BirdLife International 2014). Provided the estimate of 6 000-10 000 mature individuals in the region by Cohen (2000) is accurate, then the decrease in the regional population over the past three generations is estimated to be c. 85%. This would mean that in 1988 (3 generations ago) the estimated population would have been approximately 20 000 mature individuals, which may be an overestimate based on the amount of available habitat within the region. Accordingly, the decrease in the regional population is believed to be closer to 60% over the past three generations. The confidence in this estimate is low and requires verification.
Threats
The primary threat faced by this species is loss and degradation of its sensitive wetland habitats, brought about by drainage or damming for development and agriculture (Monadjem et al. 2003), as well as pollution. Changes in the extent of moist wetland edges and surrounding grassland (i.e. prey habitat) could be more significant than changes in the extent of permanently inundated wetland and reedbeds (CA Whittington-Jones pers. comm.) although the species may partly be able to adapt to constructed wetlands, e.g. dams and sewage works. Inappropriate burning regimes and intense grazing have also negatively affected marsh harriers (Cohen 2000). With increases in development as well as agriculture, many wetlands and other potential habitat will be drained and so this species is likely to continue to decline. Direct disturbance, especially during the breeding season when harriers are intolerant of humans, may also be a threat.
Conservation
Underway
There are currently no national conservation actions in place for this species. On a provincial scale, Gauteng, Mpumalanga, and Western Cape have incorporated the needs of African Marsh Harriers into provincial conservation plans.
Proposed
A Biodiversity Management Plan, including a Population and Habitat Viability Assessment (PHVA), is required for this species. As a priority, all wetlands that are greater than 100 ha in extent need to be identified by provincial conservation departments and prioritised for protection within future conservation plans. Included in this process must be an allowance for appropriate buffers surrounding wetlands. Projects that encourage resource stewardship of wetlands should be encouraged. The species should be included in environmental education programmes run by NGOs working around wetlands.
Research
* An accurate estimate of the regional population, including a thorough examination of habitat preferences, breeding-site selection, breeding success, and threats is urgently required.
* A tracking study to investigate the foraging requirements of this species is critical to assist conservation planners to determine suitable buffer zones on the edges of wetlands, and to identify appropriate management scales at which to conserve the species. Tracking studies of the related Black Harrier C. maurus have revealed that birds are highly mobile, and that movements are related to age-class and sex; whether the African Marsh Harrier undergoes similar movements remains to be established.
* The impact of organochloride pesticides upon this species needs to be evaluated.
