Topic : Land Birds
Article 21 07 February 2007
Olive/Karoo Thrush identification
Since the splitting of Olive Thrush Turdus olivaceus on the basis of genetic evidence, and the erection of Karoo Thrush Turdus smithi to full species level, there has been no definitive publication (field guide) to show birders in the region how to separate these birds in the field. Until new and updated field guides becomes available, these photographs show the key morphological differences to help birders separate these species. Considerable species overlap does occur in the transition region between the eastern and southern Olive Thrush and its essentially western or inland counterpart Karoo Thrush.
This is predominantly a forest loving species that also occurs on forest margins, riverine thickets and wooded parks and gardens in the moister eastern regions. The key identification features are:
- Distinct orange flanks.
- A dark patch around the nostril region of the upper mandible.
- A darker eye-ring than Karoo Thrush.
- The dark throat streaking against a whiter background giving it a bolder streaked effect than the following species.
Karoo Thrush occupies drier habitats than its eastern counterpart and in areas of overlap will choose sites that tend to be more open and less mesic than that occupied by the above species. Key field identification features include:
- Grey Flanks. There is however considerable variation in the intensity of grey plumage on the flanks. All colour forms however show some degree of grey plumage on the flanks though this may blend with shades of orange or orange/yellow.
- All-yellow upper mandible.
- Paler eye-ring than the previous species but this is not a good feature in poor light.
- Darker throat background plumage gives the effect of a less boldly streaked chin and throat.
- The extent of orange plumage on the underparts is variable.
The separation of closely related thrushes is a problem not unique to southern Africa, in fact species-level problems still exist in the taxonomy of this large family with over 330 thrushes worldwide (66 in the genus Turdus). In Africa, separation of the complex group of similar looking Olive and African Thrush Turdus pelios still poses problems and assignment of some of the subspecies to one or the other of these two species is still uncertain.