Black-capped Donacobius Donacobius atricapilla Scientific name definitions

The Black-capped Donacobius is a familiar sight in marshes and wet pastures across much of South America, often calling attention to itself with loud, duetting calls. This distinctive bird long resisted efforts by ornithologists to classify it. Formerly it was known as the "Black-capped Mockingthrush," when it was thought to belong to the New World family of thrashers and mockingbirds (Mimidae), but it now is recognized as the sole member of a family with affinities to with Old World warblers. Despite being common and widespread, and occuring in open habitats, the donacobius is little-studied; but it is known to be a cooperative breeder, at least in southeastern Peru.

21·5–22 cm; 31–42 g. Nominate race has most of head and upperparts glossy jet-black, back suffused dark brown, rump warm olive-brown; primaries and secondaries dusky black, white base of primaries (conspicuous white patch visible on both open and closed wing); rectrices black , tipped white, amount of white increasing laterally, outer rectrix two-thirds white; chin buffy white, bare patch of deep yellow on each side of throat (not normally visible except during display); throat and chest warm buffy yellow, belly deep buff-yellow, upper flanks variably barred finely black; eye bright staring yellow; bill black; legs greenish-dusky. Sexes similar. Juvenile is dusky brown, rather than black, above, with pale line behind eye , the back medium brown, edged with rufous-brown, underparts unbarred and duller than adult’s. Race brachypterus is smaller than nominate, lighter below, and with paler rump; <em>nigrodorsalis</em> is blacker on back; <em>albovittatus</em> differs from others in having prominent white supercilium.

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Editor's Note: Additional distribution information for this taxon can be found in the 'Subspecies' article above. In the future we will develop a range-wide distribution article.

Brushy areas along riversides, especially in successional vegetation in oxbow lakes; also overgrown edges of artificial water impoundments. May forage away from riversides, but breeds only in marshy areas. Sea-level to 600 m; occasionally as high as 1400 m in Ecuador.

Sedentary; in study of individually marked birds in Peru, no evidence of movement noted between suitable areas of habitat only 2 km apart (2 Kiltie, R.A. and Fitzpatrick, J.W. (1984). Reproduction and social organisation of the Black-capped Donacobius (Donacobius atricapillus) in southeastern Peru. Auk. 101(4): 804-811. Close ).

Food almost exclusively invertebrates; recorded items (Suriname) include hymenopterans, beetles (Coleoptera), orthopterans, neuropterans and arachnoids. Forages in pairs and in groups. Items usually taken from leaf surfaces, but occasionally caught in flight.

Sexes sing antiphonally, male a series of loud, ringing upward-slurred liquid whistles, “who-it, who-it, who-it”, female a lower, sizzling or grating sound; other members of co-operative group may also sing, with sex-specific song. Calls are grating scolds.

Season very protracted in N of range, Jan–Aug, peak in May–Jul; in Peru mainly in rainy season, from Oct onwards, with majority fledging in Nov–Jan. Often breeds co-operatively, pair may have up to two helpers, offspring from previous year or the year before that, which help in nest defence and in brood-feeding; unassisted pairs less successful than assisted ones. Partners display by perching close to one another while singing, bobbing the head and waving the partly spread tail sideways rhythmically; other members of a co-operative group may also sing. Nest-building apparently mainly by female, which may pilfer material from nests of other species; deep bulky cup made of vegetable fibres, snakeskins, etc., c. 10–15 cm in diameter, cup 7·5–8 cm across and 6 cm deep, situated 0·25–1 m up, occasionally to 2 m, in vegetation, frequently over water; tends to be higher up when over dry ground; territories in good habitat can be very small, often only a few metres wide and up to 100 m long. Clutch usually 2 eggs in N South America, quite commonly 3 in SE Brazil (São Paulo), eggs purplish-white, thickly covered with purplish and reddish spots and blotches; incubation by female alone, period 16–18 days; hatchling naked, with conspicuous pattern of three black spots on pink base inside mouth (almost unique among Neotropical passerines); chicks fed by both parents, also by helpers if present, adults cool them by wetting own feathers prior to brooding; fledging period 17–18 days. Success apparently dependent on presence of helpers; unassisted pairs usually fledged only one young, whereas all observed cases in which two young were reared involved pairs with helpers.

Not globally threatened (Least Concern). Generally common throughout much of extensive range; abundant in suitable habitat in some areas. May in some cases benefit from human activity, as where water impoundments are allowed to become overgrown at edges.