Rationale
(Changed due to Not applicable)
The African Grass-Owl Tyto capensis has experienced a reduction in regional population size and satisfies the population-size criterion for Vulnerable (an observed, estimated, inferred or suspected population size reduction of 30% over the last 10 years or three generations, whichever is the longer, where the reduction or its causes may not have ceased OR may not be understood OR may not be reversible). In addition, the population of less than 10 000 mature individuals is projected to decline by at least 10% within the next three generations. For these reasons, the species is listed as regionally Vulnerable.
Distribution
The species occurs in a fragmented fashion from Congo and Angola, eastwards through Democratic Republic of the Congo to Uganda, and from there southwards through southern Tanzania and Zambia to Zimbabwe and South Africa. There is a small isolated population in the highlands of Cameroon (race cameroonensis), and a larger remnant population in Kenya and Tanzania, east of Lake Victoria. Within the region, it is largely confined to areas of higher rainfall in the eastern half of South Africa. It is most commonly reported from Gauteng, KwaZulu-Natal and Mpumalanga, though significant range contraction and/or fragmentation is apparent (Mendelsohn 1997).
While historically more widespread in Free State, North West and Limpopo, the species is now known from only a few widely scattered localities in these provinces (Mendelsohn 1997). The African Grass Owl persists at low densities, but may be under-recorded, in Eastern Cape where it is found between the Lesotho border and East London. A small and isolated remnant population occurs in Western Cape, with occasional reports from the Wilderness Lakes area and in the vicinity of Bredasdorp. There is a single record for the Northern Cape (Birds in Reserves Project database). There are no recent records for Lesotho where the species was once common (Bonde 1993) and only one record for Swaziland (SABAP2).
The species is habitat-specific, and only a proportion of its distribution represents suitable ecological conditions. A basic model of African Grass Owl habitat, generated for Gauteng using high-resolution land-cover data, showed that a maximum of 25% of rural Gauteng potentially comprised suitable habitat for the species (CA Whittington-Jones and P Compaan unpubl. data). Applying this threshold regionally reduces the estimated AoO to less than 29 000 km2.
Population
The global population size has not been quantified (BirdLife International 2014). Density estimates of one bird/2-6 km2 was generated for Suikerbosrand Nature Reserve, Gauteng during 2009-11 based on intensive surveys of wetland and grassland habitat in various stages of succession (Whittington-Jones 2010). Extrapolation across the region provides a regional population of 5 000-15 000 individuals. While the densities estimated for Suikerbosrand in the late 1970s are relatively low compared to those for the Settlers area of Limpopo Province (Mendelsohn 1989), they are the only recent data available for this species. Nest survival is reportedly high, with 2-3 chicks fledging per nest (Kemp 2005) and it is therefore possible that 50% or more of free-flying African Grass Owls recorded for Suikerbosrand Nature Reserve towards the end of the breeding season were immature birds. Based upon this, the regional estimate for mature individuals has been adjusted to 2 500-7 500 birds.
Population trend
The species is believed to have undergone a reduction in population size of greater than 30% in the past three generations and is projected to decline by at least 10% within the next three generations. However, in the absence of more detailed historical population data, the rate of population decline is difficult to estimate accurately.
Threats
The primary threat to the African Grass Owl in the region is loss of habitat. Between 1994 and 2005, the combined footprint of urbanisation, afforestation, mining and cultivation in the three provinces that comprise the remaining core of the African Grass Owl's range in South Africa, i.e. KwaZulu-Natal, Mpumalanga and Gauteng, increased by an estimated 8.5%. The extent of potential African Grass Owl habitat affected remains to be assessed, but loss of wetland and associated grassland habitat is expected to exceed 20% in the next three generations. In support of this somewhat speculative suggestion, in Mpumalanga alone development applications between 2005 and 2010 covered 72% of the province. Applications were primarily for prospecting and mining for coal and covered 90% of areas in the province regarded as having high importance for groundwater re-charge and 80% of those areas with high importance for water run-off, thus increasing the probability that African Grass Owl habitat will be affected.
Fire and grazing are important tools for the management of grassland and wetland habitats, but regular heavy grazing pressure and too frequent burning prevent the development of rank grassland habitat required by African Grass Owls (Brooke 1984, Jansen et al. 1999). Their habit of nesting on the ground makes eggs and chicks vulnerable to fire and trampling by livestock (Tarboton and Erasmus 1998, Whittington-Jones 2010). Wetland drainage schemes and incompatible farming practices may explain the apparent absence of this species from Lesotho, much of Eastern Cape (Brooke 1984) and more recently from large areas of its former range in the rest of South Africa. In a slightly more positive vein, given that it is nocturnal and roosts in tall, dense grass during the day, under-recording is a problem. The species frequently hunts along road verges (Ansara 2004), where it is likely preying on rodents attracted to grain spilled by passing trucks. Consequently, African Grass Owls are frequently killed by vehicles at night, and are well-represented in museum collections. Collisions with vehicles are a significant cause of direct mortality: 27% of the 554 owl carcasses recovered from portions of two roads in Gauteng between October 2001 to September 2003 were those of African Grass Owls (Ansara 2004). Entanglement with barbed-wire fences is another potentially significant, but poorly documented cause of mortality.
Conservation
Underway
Currently, there are only limited, incipient measures that are linked to basic research. In 2009, the Endangered Wildlife Trust established the African Grass Owl Task Force. This body draws on the expertise of stakeholders to conduct research, gather information, and create awareness to further conservation of the species. Examples of such initiatives include ongoing research into spatial requirements of the species, targeted surveys of suitable habitat and collation of published and unpublished distribution data for use in land-use planning, annual monitoring of selected populations, and collection of mortality data to assist in identification of emerging threats.
Proposed
Viable habitat patches that are still known to support African Grass Owls must be mapped and incorporated into relevant regional conservation plans. Fire and livestock grazing regimes that are compatible with the habitat requirements of the species must be determined and effectively communicated to land managers. A Species Management Plan is recommended.
Research
* The apparent decline in the AoO of this species over the past three generations needs to be confirmed through appropriate surveys of remaining suitable habitat in areas where the species occurred historically, but has not been recorded in the past two decades.
* The location, design, and long-term management of roads requires investigation in order to reduce collisions with vehicles by African Grass Owls (and other owls).
