Already classified as Vulnerable in South Africa, the population of African Grass Owls in the country numbers less than 5 000 birds (Roberts Birds of South Africa, Ed VII).  As results from the latest South African Bird Atlas Project are collated, it appears that long-term survival prospects for this unique and special owl are bleak – and its Red Data List category may move to Endangered or Critical.  Once a locally common breeding resident, it is now uncommon to rare over much of its range and has disappeared altogether in some areas.

One of the problems is that the African Grass Owl has very specific habitat requirements.  They occur in relatively high rainfall regions (in South Africa that means regions with around 800 mm/year).  They prefer treeless areas associated with damp substrata such as marshes and vleis, favouring patches of tall rank grass, sedges or weeds.  They are also found in dense ground cover in thorn scrub, low fynbos or renosterveld close to water and among thick stands of grass and sedge. 

This grassy habitat is important for these owls, which are nocturnal.  When flushed during the day, they fly a very short distance before dropping back into grass cover.  Their roost site develops into a series of “caves” in the grass, interconnected by tunnels and open landing platforms.  While hunting at night, they rest on the ground, returning at intervals to the roost site.  Hunting forays are only 10% successful.  Their favourite food consists of large vlei rats; about 76% – 98% of the diet consists of rodents of various kinds although they also eat shrews and birds.  In some areas of the Western Cape, the bird has been recorded as taking up to 13 different types of prey.

Their breeding habits are little known.  They are monogamous, possibly territorial and solitary nesters.  The nest consists of an unlined hollow in the ground situated in rank grass, usually at the end of one of the long tunnels the bird makes in the grass.  The nest often evolves from or into the roost site and the nest may be re-used.  Laying dates in South Africa are from March to April.  While nest survival is high, only 2 – 3 chicks survive (up to six eggs may be laid).  Nests are vulnerable to fires.

The African Grass Owl’s habitat preference is believed to be the cause of its woes as rank grass habitats are subject to a variety of environmental pressures including: trampling and overgrazing by domestic livestock, fires (both natural fires and those created by farmers wanting to increase their grazing) as burning does not allow the development of the tall rank grass favoured by these owls, alien invasive plants and trees which encroach on wet areas adversely affecting the amount of water available for wetland sustainability, agriculture, collision with fences and road casualties.  To make matters worse, unlike many other threatened species, the African Grass Owl is not well represented in protected areas. 

According to BirdLife South Africa, the long-term survival of this species will probably depend on the success of the Important Bird Areas programme.  The African Grass Owl needs to be closely monitored and would benefit from the conservation of its habitat.

Rank grass areas in regions such as Wakkerstroom (which we visit on our Birding Hotspots Tour) provide ideal African Grass Owl habitat.

Source:  Roberts Birds of South Africa, Ed VII; BirdLife South Africa Newsletter (Oct 2009)