Rationale
(Changed due to Not applicable)
As is the case in several other river specialists, the Half-collared Kingfisher Alcedo semitorquata is suspected to have undergone population declines due to a reduction in the extent and quality of its sensitive riverine habitat. Declines appear to approach 30% over the last 10 years, and the regional population is suspected to be fewer than 10 000 mature individuals, occupying a range that may be greater than 2 000 km2, qualifying the species as Near Threatened.
Distribution
Endemic to sub-Saharan Africa, occurring in three isolated sub-populations (but with some records of vagrants in intervening areas), namely Ethiopia, north-western Tanzania, and south-central Africa. In the latter region, it occurs from southern Tanzania, Zambia, Malawi and Angola southwards to northern Namibia, Zimbabwe, Mozambique and South Africa. Surprisingly, it is absent from the Okavango Delta in Botswana, but it does occur on the Kavango River in Namibia (Clancey and Herremans 1997). In Zimbabwe it is restricted to the northern and eastern parts of the country, contiguous with the population in central Mozambique; in southern Mozambique it historically occurred sparingly on the streams of Lebombo Mountains near the Swaziland border (Clancey 1996), but was not recorded south of the Save River by Parker (1999). It avoids the Limpopo Valley, corresponding to the border between the South African nominate subspecies and the northerly subspecies tephria (Clancey and Herremans 1997).
Within the region, the Half-collared Kingfisher is widespread but generally sparsely distributed throughout high-rainfall areas of the east and extreme south (Fry et al. 1988, Allan 2000). Atlas data indicate strongholds in the Bushveld-Highveld interface in Gauteng, the Mpumalanga/Swaziland Escarpment region, uplands of KwaZulu-Natal and coastal zones in Eastern Cape (Tarboton et al. 1987, Clancey and Herremans 1997). In Western Cape it is rare west of George, but is occasionally recorded as far as Cape Town and the Cederberg. It may occur marginally in Lesotho, but is generally absent from that country, despite being relatively common in adjacent areas of the Drakensberg in KwaZulu-Natal and the eastern Free State. SABAP2 data suggests an AoO of c. 109 000 km2, but only approximately 1-2% of this area represents its highly localised and specialised riverine habitat; the effective range of the species may therefore be in the order of 1 100-2 200 km2.
Population
The global population size has not been quantified, but the species is reported to be widespread and locally common (del Hoyo et al. 2001). It is generally uncommon even in prime habitat with breeding pairs spaced at least 1 km apart (Clancey 1996). Because the species is widely perceived as rare and elusive (with a SABAP1 mean reporting rate for range of only 4.1%, compared to e.g. 15.8% for Malachite Kingfisher A. cristata), actual declines in population and range can easily be overlooked. Because of its specialised habitat requirements only a small proportion of its range constitutes suitable habitat, and territories are widely spaced even in seemingly ideal conditions. Given a range of 1 100-2 200 km2, and assuming linear riverine territories encompassing 1 km of river (plus buffer zones of riparian vegetation extending to 50 m on either bank), a crude calculation suggests the population may be in the order of 11 000-22 000 pairs. However, actual numbers are probably much lower, e.g. only seven were counted along 61.5 km of the Komati River in Swaziland, i.e. 1 bird/8.8 km of river frontage (Allan 2000). The regional population may thus number less than 10 000 mature individuals. Confidence in this estimate is low.
Population trend
Globally, the Half-collared Kingfisher has declined owing to pollution, river siltation and habitat destruction (BirdLife International 2014). The regional population is also suspected to be experiencing a decline, as revealed by bird atlas data (although this decline is suspected to not attain the 30% threshold). Relative abundance data presented by Clancey and Herremans (1997) sparked concerns about a marked decrease, particularly in KwaZulu-Natal where coastal populations appear to have declined drastically compared with areas to the immediate south in Eastern Cape (Clancey 1992, Allan 2000). This decline may have become more widespread and severe, as a comparison between SABAP1 and SABAP2 data suggests a decrease of 13.3% in EoO, and 40.6% in AoO, and comparative maps show notable increases in range fragmentation over much of the region. Confidence in the population trend estimate is low.
Threats
The Half-collared Kingfisher is one of 11 South African waterbird species primarily restricted to riverine habitats; the beleaguered position of river ecosystems in South Africa is highlighted by the fact that seven of these species are considered threatened or near-threatened (Allan et al. 1997a). The Half-collared Kingfisher is threatened by widespread degradation of its specialised riverine habitats, through siltation, erosion, inflow of water containing suspended sediments, heavy metals and other pollutants, water extraction and clearing of riparian vegetation (Allan 2000). Due to the linear connectivity of its habitat, consequences of detrimental factors are not limited to the point of impact but also occur downstream. Likewise, dams and other impoundments may have major ecological impacts downstream, through reduced river flow, attenuated flood peaks, and altering seasonality and temperature of flow, sediment loads, channel morphology and water chemistry (Barnes 2000). Species adapted to fast-flowing, clear and relatively nutrient-poor ecosystems, such as the Half-collared Kingfisher, are particularly vulnerable to algal blooms caused by eutrophication by run-off from agricultural and mining activities, sewage works and other sources. Changes in river catchments, including alien plant invasion, irrigation, over-abstraction, human settlement and overgrazing have reduced natural run-off and groundwater levels substantially (Barnes 2000). Availability of suitable banks for construction of nest tunnels may be a further limiting factor for this species. It is unknown whether infestation of waterways by alien fish constitutes a threat.
Conservation
Underway
No conservation measures are currently underway.
Proposed
Given its specialised habitat requirements, the Half-collared Kingfisher is of great value as an indicator species for the quality of river ecosystems throughout its range, particularly in a region with an overall scarcity and ever-increasing demand for water. A full census of representative river systems should be conducted, which could simultaneously contribute to population estimates of co-occurring threatened species such as White-backed Night-Heron Gorsachius leuconotus and African Finfoot Podica senegalensis. Whittington-Jones (2011) proposed a target of 240 pairs for Gauteng rivers, and indicated that considerable restoration work will be required given the poor state of rivers in the province. While local conservation efforts are commendable, the long-term conservation of the Half-collard Kingfisher, and a host of other aquatic and riverine species, will ultimately depend on effective management, conservation and restoration of rivers at the ecosystem-level through national, provincial and municipal initiatives.
Research
* Conduct surveys of river systems to obtain a more accurate estimate of population size and habitat requirements.
* Assess impacts of human-induced modification to rivers on this species and other riverine specialists.
