Voice
Song is a stereotyped crescendo , starting as a soft series of warbling notes, building in volume, pace and pitch, then ending with a loud 'wheeeooo'. Also a nasal 'where'.
Cape Grassbird (Sphenoeacus) [XC280671]
by Peter Boesman from Kurisa Moya, Tzaneen, Limpopo, South Africa (song)
Cape Grassbird (Sphenoeacus afer) [XC512626]
by Frank Lambert from Cape of Good Hope NP, Western Cape, South Africa (song)
Subspecies
Has sometimes been linked in a superspecies with Moustached Grass-warbler (Melocichla mentalis) and Rockrunner (Achaetops pycnopygius), now classed as a babbler (Timaliidae). Now thought not to be closely related.
The following 4 subspecies are recognised:
excisus Clancey, 1973 - Eastern Zimbabwe highlands and adjacent Mozambique.
natalensis Shelley, 1882 - North-eastern South Africa (Northern Province south to northern and eastern Free State and KwaZulu-Natal), western Swaziland and northern Lesotho.
intermedius Shelley, 1882 - Eastern South Africa (extreme southern KwaZulu-Natal and eastern Cape south to former Transkei); probably also southern Lesotho.
afer (Gmelin, 1789) - Western Cape and south-western eastern Cape (east to about R Gamtoos), in south-western and southern South Africa.
BirdLife International Species Factsheet