Oenanthe dubia (Blundell & Lovat, 1899)

Dove, Carla J., Whatton, James F., Milensky, Christopher M., Boss, Will, Rayaleh, Houssein & Awaleh, Djama G., 2024, Notable records and observations of four passerines in Djibouti, 2020, Bulletin of the British Ornithologists’ Club 144 (1), pp. 42-48 : 43-44

SOMBRE ROCK CHAT Oenanthe dubia

Generally recognised as an Ethiopian endemic, but one historical specimen, together with sight records in 2010 and 2012, near Mt. Wagar, north-west Somalia ( Clement & Rose 2015), suggest that it may be more widespread and thus only near-endemic. A first sight record from Djibouti in September 2010 ( Borrow & Jama 2010) was reported as a possible vagrant by Clement & Rose (2015). Sombre Rock Chat is commonly seen in Dittilou by local people ( HR pers. obs.) and was frequently seen by us there, with several mist-netted on 17‒19 March 2020, including juveniles, and males and females in breeding condition (per gonad measurements). Dittilou (c. 700 m) is one of the wettest areas in Djibouti with annual rainfall exceeding 400 mm. The main vegetation in higher areas consists of Terminalia ( Terminalia brownii ), boxwood ( Buxus hildebrandtii ), acacias ( Acacia etbaica , A. millifera ) and scattered large Sycamore Figs ( Ficus sycomorus ). In lower basaltic cliff areas, Camphor Bush ( Tarchonanthus camphoratus ) and Red Acacia ( Vachellia seyal ) replace boxwoods. Multiple family groups of Sombre Rock Chats were observed in rocky wadis lined with trees (canopy height 10‒15 m), often perched on large boulders and unwary of humans. Adults were observed feeding begging young and one family group included two juveniles. Elsewhere, Sombre Rock Chat inhabits arid rocky areas with scattered bushes and lava fields at 740‒1,800 m ( Redman et al. 2016, Collar & Sharpe 2020). The species regularly occurs above 900 m in Djibouti ( HR pers. obs.). We separated adults from Brown-tailed Chat Cercomela scotocerca , which could occur in the same area, based on the much darker undertail-coverts (brown not white; Clement & Rose 2015). Two juveniles (one skin, USNM 664495, and one fluid-preserved, USNM 664532) were obtained, and were found to differ morphologically from the plumage described in Clement & Rose (2015) based on a photograph of an immature in northern Somalia. Our specimens were associating with adults and match well three photographs labelled juvenile submitted to eBird (C. Burne, http://ebird.org/ebird/view/checklist/S61732820; accessed 19 April 2023) on the northern shore of Lake Basaka, Oromia, Ethiopia. We describe the juvenile plumage from these two specimens as follows ( Fig. 1 ; photographs may appear to differ slightly from the following description due to lighting effects). Head brown, slightly browner ear-coverts with buffy-spotted tips, narrow pale incomplete eye-ring, upperparts spotted buffy, sometimes with dark brown tips. Greater primary-coverts and alula quills edged pale whitish grey. Greater secondary-coverts tipped dark buff brown. Median secondary-coverts brown with light buffy tips. Tail dark brown with buffy tips. Throat pale grey, breast scalloped pale buff with brown tips, belly pale with some scalloped dark tips. Undertail-coverts rusty brown with darker rachises. Bare parts: iris, dark brown; bill, dark brown; tarsi and feet, dark brown with silvery sheen.

Specimen USNM 664495 was mist-netted on 17 March 2020 and determined to be a juvenile based on the plumage characteristics described above and gonad measurements (testes, L = 1.0 × 0.5 mm, white; R = 1.0 × 0.5 mm, black), with bursa (9 × 4 mm). Specimen USNM 664532 had identical plumage, but gonad measurements were unavailable due to specimen preparation type. These are the only known juvenile-plumaged birds in collections. In addition, four adult males (enlarged testes and seminal vesicles, collected 17‒19 March 2020) and one adult female (ovary in laying condition, largest ovum 10 × 10 mm, collected 18 March 2020) were in breeding condition. Stomach analysis found them to contain insects or to be empty. Most specimens were in body and/or tail moult. One aberrant-plumaged male specimen in breeding condition, USNM 664494, had numerous white feathers on the head, back, breast and wing-coverts (Fig. 2).

Juveniles have also been observed in gardens in Arta, and this species is frequently seen in Assamo, Dikhil, Galafi and at Ghoubet windfarm (HR pers. obs.). These observations, together with the specimen data, prove definitively that the species breeds in Djibouti and is locally common.

Figures

Figure 1 (A‒B). Juvenile-plumaged Sombre Rock Chat Oenanthe dubia, specimen USNM 664495, alongside adult-plumaged (C) specimen USNM 664496 (James Whatton)