diagnostics

34-37 cm, 420 g. An inconspicuous and relatively quiet ground-roosting owl of wetlands and open grassland. Most likely to be confused with syntopic Marsh Owl Asio capensis but much less likely to be seen during daylight hours, unless disturbed. The sexes are alike. Heart-shaped, densely feathered facial disc white, contrasting with dark, teardrop-shaped eyes but not with whitish bill. Upperparts dark olive-brown, each feather with tiny white spot at tip. Underparts white to pale buff, with scattered dark spots. In flight shows grey-brown remiges crossed by three narrow dark bars; tail dark centrally, grading to white on outer rectrices. Legs feathered buff; feet greyish. Juveniles are darker than adults at fledging, and lack white dorsal spots Kemp (2005). A buff or rufous coloured facial disc is considered by many authors to further distinguish juveniles from white-faced adults, but is not a reliable trait as there are several recent records of rufous-faced individuals breeding (MD Pretorius pers. comm.).

trophic

African Grass Owls appear most concentrated in areas with rainfall of 700-800 mm per year (Tarboton and Erasmus 1998) and have been recorded at altitudes from sea-level to 1 900 masl. As its name implies, the species typically roosts and breeds in tall, rank grass or sedges associated with damp substrates such as permanent and non-perennial wetlands and streams (Tarboton et al. 1987, Kemp 2005), although it will breed in any area of long grass and is not exclusively associated with wetlands. It constructs a series of tunnels, caves and landing platforms around the nest and roost, and therefore requires tall grass that offers concealment from above, and has relatively rigid but pliable blades, such as the grass species Imperata cylindrica. In paired birds, the male and female roost apart. Along wetland edges, Grass Owls may roost in close proximity to Marsh Owls, but are often outnumbered 10:1 by that species. The peak breeding season (February-April) coincides with maximum grass cover.

At night it may hunt over drier and more open habitats near its wetland roost sites, but still prefers hunting in tall grassland to short grassland, wetlands or croplands (Kemp 2005). However, being opportunistic hunters responsive to rodent outbreaks, African Grass Owls may hunt or even breed in sub-optimal habitats in years of high rodent abundance. Such habitats include sparse woodland (Mendelsohn 1989), scattered thorn scrub with dense ground cover, old fields (Tarboton et al. 1987, Kemp 2005) and planted pasture (CA Whittington-Jones pers. obs.). Western Cape populations are found in Fynbos (Dean and Dowsett 1986) or Renosterveld (Cameron 1999), usually near water in thick Stenotaphrum grass or Juncus sedges. Birds in otherwise atypical habitats may represent wandering non-breeding adults or dispersing immatures. The generation length of six years is the mean of two calculated values derived from published and/or extrapolated estimates of mean age at first breeding, maximum longevity in the wild and mean annual adult survival (BirdLife International 2014).