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Black-tailed Leaftosser Sclerurus caudacutus Scientific name definitions

J. V. Remsen, Jr.
Version: 1.0 — Published March 4, 2020
Text last updated January 1, 2003

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Introduction

The Black-tailed Leaftosser is a member of the genus Sclerurus distributed throughout much of Amazonia. An isolated population is found in the coastal forest of southeastern Brazil. The leaftossers are now considered closely aligned with the miners, genus Geositta, within the Furnariidae, but have sometimes been elevated to their own family. Many of the species are widespread with considerable overlap, and best identified in the field by vocalizations. Black-tailed overlaps with both Tawny-throated Leaftosser (Sclerurus mexicanus) and Short-billed Leaftosser (Sclerurus rufigularis), but is generally larger, longer billed (than Short-billed), and is darker with a somewhat contrasting white throat in comparison to the two. Despite its common name, the Black-tailed Leaftosser does not have an appreciable blacker tail than other leaftossers, a feature that would be almost impossible to see in the field for identification purposes. Leaftossers are quite secretive birds of the forest, found as singles or pairs. They forage on the forest floor, but often sing from a low branch or root, and are typically very vocal at dawn and dusk. As in other species of leaftosser, they emit a loud “squeak” when startled. Little is known about the natural history of leaftossers. Geographical variation of both song and plumage suggest that the taxonomy of this species, and leaftossers in general, is complicated and worth studying.

Field Identification

16–18 cm; 34–42 g. The darkest and dullest Sclerurus. Nominate race has face dark rufescent brownish, faint scalloping in malar area; crown dark brown, slightly darker feather margins producing faintly scalloped look, faint rufescent tones on forehead; back to uppertail-coverts very dark reddish-brown; wings nearly uniform dark reddish-brown; tail rounded, broad, shafts of rectrices stiffened, tips sometimes lacking barbs for distal 1–2 mm, sooty blackish, hints of dark reddish-brown in some outer webs; throat whitish with faint dark lower margins, blending into mainly dark rufescent breast (some continuation of throat pattern on uppermost breast), and to almost blackish-brown rest of underparts; iris brown to dark brown; upper mandible black to blackish-brown, lower mandible usually bicoloured, with pale grey, creamy or pinkish base and grey to black tip; tarsus and toes black to dark brown. Sexes alike. Juvenile is slightly darker throughout, has smaller, duller throat patch with darker feather margins. Race insignis is described as like nominate but upperparts duller, less rufous-brown; brunneus is slightly paler, more olivaceous throughout, throat duller with broader, more brownish (less blackish) margins, variable, more reddish in N of range, legs sometimes dull reddish-tinged; pallidus is paler in general coloration, throat white with dusky tips, breast and face ochraceous brown (not dark brown); umbretta is like nominate but throat feathers pure white, each feather with dusky tip, chest duller, less rufescent, lower breast and belly browner (much darker overall than nearest Amazonian races).

Systematics History

Editor's Note: This article requires further editing work to merge existing content into the appropriate Subspecies sections. Please bear with us while this update takes place.

Sister-species to S. guatemalensis, based on plumage similarities and parapatric ranges, recently corroborated by phylogenetic analysis (1). Validity of race insignis, described from a single locality, seems questionable. Dark race caligineus overlooked in HBW. Geographical distribution of races, particularly N of R Amazon, not well understood, and individual variation in many of the characters used to describe most of them may lead to substantial revision of boundaries; specimens from R Purus (W Brazil) intermediate between pallidus and brunneus; proposed race olivascens (SC Peru) apparently not diagnosable, and probably represents clinal variation within brunneus (specimens from SW Amazonia less reddish on average than those farther N). Critical revision of races and their boundaries badly needed. Six subspecies recognized.

Subspecies


SUBSPECIES

Sclerurus caudacutus caudacutus Scientific name definitions

Distribution

the Guianas and NC Brazil (Amapá) (2).

SUBSPECIES

Sclerurus caudacutus insignis Scientific name definitions

Distribution

NW Pará and perhaps more widespread in N Brazil N of R Amazon.

SUBSPECIES

Sclerurus caudacutus brunneus Scientific name definitions

Distribution

Tropical se Colombia to Peru and w Amazonian Brazil

SUBSPECIES

Sclerurus caudacutus olivascens Scientific name definitions

Distribution

E Peru (Ayacucho) to extreme n Bolivia (Pando)

SUBSPECIES

Sclerurus caudacutus pallidus Scientific name definitions

Distribution

C Brazil S of R Amazon (E from at least R Madeira to W Maranhão).

SUBSPECIES

Sclerurus caudacutus umbretta Scientific name definitions

Distribution

Coastal e Brazil (Alagoas to Espírito Santo)

Distribution

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.

Habitat

Tropical lowland evergreen forest; terra firme. From near sea-level to 500 m; locally to 950 m in E Ecuador and to 1100 m in Venezuela.

Movement

Resident.

Diet and Foraging

Invertebrates; cockroach (Blattodea) oothecae, also Coleoptera, annelid worms and ants reported. One record of a fallen fruit eaten. Usually observed singly. Terrestrial; hops on ground, does not walk. Gleans and probes ground and leaf litter; flakes litter to expose prey.

Sounds and Vocal Behavior

Song a series of 10–12 loud, ringing, descending “kweet” or “whee” notes, usually introduced by low sputtering trill; call a sharp “skweeup”.

Breeding

Nestlings in Jun in S Peru. Monogamous. Nest a shallow cup c. 13 cm in diameter, made of leaf petioles, placed in enlarged chamber at end of straight tunnel 50 cm long, probably excavated by the birds themselves, in dirt bank; estimated territory size 18 ha. Clutch 2 eggs; both parents feed nestlings.
Not globally threatened. Uncommon to locally common. Estimated densities of 6 birds/km2 in transitional forest in SE Peru and 5–10/km2 at four terra firme sites in French Guiana. Occurs in a number of protected areas, e.g. Imataca Forest Reserve and El Dorado, in Venezuela, Cuyabeno Reserve, in Ecuador, and Cristalino State Park, in Brazil. Disappears from fragmented or selectively logged forests.
Distribution of the Black-tailed Leaftosser - Range Map
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Distribution of the Black-tailed Leaftosser

Recommended Citation

Remsen, Jr., J. V. (2020). Black-tailed Leaftosser (Sclerurus caudacutus), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.bltlea1.01
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