SPECIES

Swynnerton's Robin Swynnertonia swynnertoni Scientific name definitions

Flemming P. Jensen
Version: 2.0 — Published February 4, 2022

Plumages, Molts, and Structure

Plumages

Natal Down

The nestlings have pink skin with dark gray down and bright yellow gape (1).

Juvenile

The juvenile plumage (from fledging to about 4 months of age) is brown or rufous above, with buffy yellow spotting over the eyes, nape and mantle, and on upperwing coverts (1). The underside is like that of the adult, but paler with buff streaks on flanks, chin light buff, and crescent on foreneck pale creamy and dark brown and with the breast pale yellow, and with the feathers tipped brown and the belly mottled gray-white (1).

Immature

At about 6 weeks of age, juveniles begin to molt into immature plumage (1). This plumage resembles the adult female but retains the juvenile flight feathers and some pale-tipped greater coverts, and has pale gray throat and paler yellow breast (2). In Zimbabwe, the immatures molt to adult plumage at 13–15 months, starting with the flight feathers (3).

Adult

Male. Head and hindneck uniform gray; mantle to uppertail coverts olive-brown; wing-coverts and flight feathers slate-gray with a slight olive-tinting to all wing feathers, primaries finely edged paler, and secondaries and tertial edges light olive; tail uniform slate-gray. Below a rich orange-yellow breast with flanks tinged olive, becoming paler in the belly with buff or white undertail coverts. The center of the lower throat has a narrow crescent of white, bordered black on the lower edge, that separates the orange-yellow breast from the gray throat.

Female. Similar to male but duller with crown, face and neck tinged dark olive and chin and upper throat paler or buffy gray.

Molts

At approximately 6 weeks of age, juveniles molt into immature plumage which is completed by 3 months (3). At 13–15 months, birds in immature plumage molt into adult plumage, beginning with the primaries (3). In Zimbabwe, primary molt has been recorded in immatures and adults from November and December to February and March; individuals recaptured during this period suggested a 3-month molt period (1, 3).

Bare Parts

Bill

Black in adult. In juvenile, the upper mandible is dark horn and the lower mandible is paler for the first few months, but gradually darkens (1).

Iris

Dark brown in adult. In juvenile, iris tinged gray for first 3–4 months (1).

Tarsi and Toes

Legs and feet pale grayish-pink in adult. In juvenile, legs and feet pinkish, paler than in adult (1).

Measurements

East Usambara Mountains (Tanzania)

Mean wing length, unsexed 67.7 mm (range 67.0–69.0, n = 6) (4).

Mean mass, unsexed 15.9 g (range 14.9–18.0, n = 5) (4).

Udzungwa Mountains (Tanzania)

Mean wing length, female 69.0 mm (range 65.0–73.0, n = 6) (FPJ, unpublished data).

Mean wing length, male 72.5 mm (range 71.0–74.0, n = 6) (FPJ, unpublished data).

Mean wing length, unsexed 70.5 mm (range 65.0–75.0, n = 11) (FPJ, unpublished data).

Mean mass, female 17.0 g (range 15.5–18.5, n = 5) (FPJ, unpublished data).

Mean mass, male 16.5 g (range 14.5–18.0, n = 5) (FPJ, unpublished data).

Mean mass, unsexed 17.5 g (range 15.5–20.5, n = 9) (FPJ, unpublished data).

Bvumba Highlands (Zimbabwe)

Mean wing length, female 67.3 mm (range 65.0–70.0, n = 41) (1).

Mean wing length, male 70.4 mm (range 66.0–73.0, n = 106) (1).

Mean mass, female 16.3 g (range 14.4–19.5, n = 44) (1).

Mean mass, male 15.8 g (range 13.8–20.4, n = 105) (1).

Eastern Highlands (Zimbabwe)

Mean wing length, female 66.9 mm (range 63.0–70.0, n = 59) (3).

Mean wing length, male 70.8 mm (range 66.0–75.0, n = 87) (3).

Mean mass, female 16.1 g (range 13.6–19.5, n = 64) (3).

Mean mass, male 15.8 g (range 13.6–20.4, n = 91) (3).

In a sample of 389 birds from Zimbabwe, adult males had longer wings and tail than females (P < 0.001), but sexes did not differ in body mass (3). Adults also had longer wings and tail than immatures (P < 0.001), whereas young still dependent on their parents were slightly heavier than those in early independence (3). After the first partial molt, wing length increased by 2–5 mm (mean 3.5) in males (n = 9), and by 2–4 mm (mean 2.6) in females (n = 8) (3).

Recommended Citation

Jensen, F. P. (2022). Swynnerton's Robin (Swynnertonia swynnertoni), version 2.0. In Birds of the World (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.swyrob1.02