Imagine you are busy birding and walking in a field with low shrub vegetation in the southern Free State or in the Central Karoo and your attention is drawn to a constantly high pitched tee-tee-tee bird sound near you. Suddenly a small prinia-like bird with a long tail flies out of a low bush or runs like a mouse in front you. This bird is likely to be the elusive Rufous-eared Warbler…
The Rufous-eared Warbler, or Malcorus pectoralis, is a small prinia-like bird of the family Cisticolidae, weighing a mere 10 grams, which occurs mainly in the Karoo, arid to semi-arid shrublands, as well as in old cultivated fields or overgrazed grassland with low shrub species. The Rufous-eared Warbler’s distribution in the field is very similar to the overlapping Karoo and Black-chested Prinias and Grey-backed Cisticolas, which can share the same habitat in some areas. The warblers are very attractive, occurring mostly singly or in small family groups, and are sometimes difficult to spot as they feed low in the bush or on the ground in the scrubby vegetation, and are only seen when flying low or even running (like mice) to the next bush clump. They also like to perch on fence lines in its preferred habitat.
This species has adapted to the semi-arid vegetation, which is unsuitable for agriculture, and is often seen in vacated cultivated fields that has been taken over by low shrub species. Therefore, the Rufous-eared Warbler can possibly be regarded as an indicator for disturbed and overgrazed veld in some areas of its distribution range. No major differences in the species distribution have been noted between the two South African Bird Atlas Projects of the late 1980s – early 1990s and the current project, which started in mid-2007, although its range seems to get expanded to Gauteng, and the birds are also becoming more common in the western Lesotho and in the Rosendal – Paul Roux – Lindley areas of the central-eastern Free State, possibly due to changes in the veld conditions making the habitats suitable for Rufous-eared Warblers. In these areas the birds mostly prefer a poorly managed grassland invaded by Felicia filifolia subsp. filifolia (Persbergdraaibos).
Rufous-eared Warbler diet, behaviour and vocalisations
This species mostly forages on the ground or in low shrubs searching for insects on the stems and leaves, but also consumes small fruits and seeds of Wild Asparagus, Honey-thorns and alien creeping salt bushes. Diet studies based on the stomach contents by the late Dr Richard Dean in the Central Karoo (Prince Albert) revealed mainly invertebrates such as weevils and other beetles, caterpillars, several ant species, spiders and even ticks, to name a few. The birds typically occur in small family groups. During the breeding season the male mostly sits on top of a bush and gives its monotonous tee-tee call repeated for long periods and audible from afar. Their breeding season usually lasts during the summer months between September – December, but the egg laying can commence after a good rainfall in some areas and breeding can be initiated in any month, even during the late winter. When the incubating female is disturbed from her nest, she will flee by running from the nest rather than flying away as other birds mostly do.
The Rufous-eared Warbler builds a small, oval nest with a side-top entrance. The nest is woven with grass leaves, stems and silky bark, bound with spider web and lined with plant down, mostly fluffy seeds of Karoo Rosemary in the Central Karoo. The nests are situated less than a metre above the ground in the bush, with some being at as low as 20 cm high. When selecting nest sites, the birds prefer the Driedoring shrubs, but may also choose other shrub species such as Pteronia (Resin Daisies), Rosinia (Doringvygie) and Galenia (Bloubrakbossie), depending on the area. The eggs are laid in clutches of 3 or 4 and hatch after 12–13 days; the young are fledged and ready to leave the nest in 11–13 days. The nestlings are fed by both parents with mostly small grasshoppers and caterpillars. The Rufous-eared Warbler nests are also exposed to predators such as snakes, mainly Common Egg-Eaters, which prey on the eggs.
Plumages and geographical variation of the Rufous-eared Warbler
As its name suggests, the bird has a bright rufous face patch, a white throat and a black breast band, of which the face patch is brighter in males and the throat band is narrower in females. In some individuals, the breast band can also be reduced or absent during the winter months. Their long, slender and graduated tail feathers, with buff edges on the outer webs, are often held cocked and are diagnostic. Some geographical variation occurs in the plumage of this warbler, manifesting mainly in the paleness of the underparts, the width of the pectoral band, the presence or absence of streaking on its flanks, and in the intensity of its back plumage streaking. Based on these differences three subspecies, or geographical variations, are recognised, namely M. p. pectoralis, M. p. ocularius and M. p. etoshae:
- The nominate subspecies, or “ p. pectoralis”, occurs mostly in the Karoo areas of the Western and Northern Cape extending further eastwards to the Eastern Cape and northwards to the Free State, with its range limit along the line south of Kimberley – Bloemfontein – Wepener adjacent to the lowland areas of western Lesotho. This subspecies is the darkest Rufous-eared Warbler; its upperparts are brown-grey with a heavily streaked back. Their cheeks and ear coverts are rich chestnut and the breast is grey with streaking on its flanks. Their lower belly is pale buff grey with warm brown lower flanks. The pectoral band is wider than in the “M. p. ocularius” subspecies, although can vary individually.
- The “ocularius” subspecies ranges from areas north of the Kimberley – Bloemfontein – Wepener line and eastwards to the eastern Free State – Senekal – Paul Roux – Lindley, northwards to the southern Gauteng, and further west to the North West Province, Northern Cape, Botswana and Namibia south of Windhoek. This subspecies plumage is paler compared to the nominate subspecies, with its upper parts paler brown and ear coverts with a rustier golden-brown appearance. The birds of p. ocularis are also whiter on their lower belly with a narrower pectoral band (which also can vary individually) and unstreaked flanks.
- The etoshae subspecies occurs in the northern parts of Namibia, mainly north of Windhoek towards the Etosha Pan and southern Ovamboland. With their ear coverts being paler and the breast and belly feathers more creamy white, the birds of p. etoshae are considerably paler than the other two subspecies. The black pattern of the crown feathers in etoshae has wider margins than the other two subspecies.
As both the “pectoralis” and “ocularius” subspecies occur in the Free State, the Ornithology Department of the National Museum launched a project to clarify their relationships. The departmental skin collection includes specimens of previously collected Rufous-eared Warblers in different areas of the Free State, which have been measured to obtain biometric data for the comparative analysis. Additional biometric data of ringed individuals of this species will be obtained during scheduled field trips to various parts of the Free State and possibly adjacent areas in Eastern and Northern Cape. Preliminary results suggest that the “pectoralis” subspecies probably have a longer tarsus compared to “ocularius”, although further data are needed to be more certain. The chest band is also to be measured to determine if any differences exist between the subspecies, as well as between the sexes.
Furthermore, the project aims to compare the mitochondrial DNA of M. p. pectoralis and M. p. ocularis to establish the degree of their isolation and when they diverged. The molecular data can also be instrumental to clarify the phylogenetic relationships of Malcorus genus with other Cisticolidae species. Further molecular and biometric data for comparison of the two subspecies are to be obtained during field work trips to such localities around the Free State as Florisbad, Springfontein, Fauresmith, Lindley and Paul Roux.
Berruti, A. 1997. Rufous-eared Warbler. In: Harrison, J.A., Allan, D.G, Underhill, L.G., Herremans, M., Tree, A. J., Parker, V. & Brown, C.J. (Eds). The atlas of southern African birds. Vol. 2. Johannesburg: BirdLife South Africa, pp. 330–331.
Chittenden, H., Allan, D.G. & Weiersbye, I. 2012. Roberts geographic variation of southern African birds. Cape Town: John Voelcker Bird Book Fund.
Dean, W.R.J. 2005. Rufous-eared Warbler Malcorus pectoralis. In: Hockey, P.A.R., Dean, W.R.J. & Ryan, P.G. (Eds). Roberts — Birds of Southern Africa. 7th ed. Cape Town: The Trustees of the John Voelcker Bird Book Fund, pp. 849–850.
Le Roux, P.M., Kotzé, C.D., Nel, G.P. & Glen, H.F. 1994. Bossieveld. Bulletin 428. Pretoria: Department of Agriculture.
Sinclair, I., Hockey, P.A.R., Tarboton, W., Perrins, N. Rollinson, D. & Ryan, P. 2020. Sasol birds of Southern Africa. 5th ed. Cape Town: Struik Nature.
Tarboton, W. 2011. Roberts nests and eggs of Southern African birds. Cape Town: Trustees of the John Voelcker Bird Book Fund.
Image: The Rufous-eared Warbler (Malcorus pectoralis subsp. ocularius) from the Paul Roux area, Free State, showing a wider chest band. (Photo: Martin Potgieter)
Image: The Rufous-eared Warbler (Malcorus pectoralis subsp. pectoralis) from Witmoskloof, Cradock, Eastern Cape, showing a narrower chest band, which can vary individually. (Photo: Martin Potgieter)
Image: The Rufous-eared Warbler (Malcorus pectoralis subsp. etoshae) from Etosha National Park, Namibia, showing paler ear coverts and paler creamy white breast and belly feathers. The breast band is sometimes absent in individuals during the winter months as in this individual photographed on 8 July 2019. (Photo: Raphael Lebrum / Macaulay Library ML176321461, with the photographer’s and eBird permissions to reproduce in Culna)
The Rufous-eared Warbler (Malcorus pectoralis subsp. etoshae) from Etosha National Park, Namibia, which also shows paler ear coverts and more creamy-white underside with a clear breast band photographed during summer. (Photo: Christien Boshoff)