Birds of North and Middle America, part V/Genus 14. Microbates Sclater and Salvin

by Robert Ridgway

 

Genus MICROBATES Sclater and Salvin.

Microbates^[1] Sclater and Salvin, Nom. Av. Neotr., 1873, 155. (Type, M. torquatus Sclater and Salvin = Rhamphocænus collaris Pelzeln.)

Very small, long-billed, long-legged Formicariidæ, similar in appearance to Rhamphocænus but with shorter and broader bill, longer tarsi, relatively longer toes (especially the hallux), narrower nostrils with differently shaped operculum, and much shorter tail (only about half, instead of four-fifths) as long as wing.

Bill about as long as head, nearly straight, its width at latero- frontal antiæ much greater than its depth at same point and equal to much more than one-third the distance from nostril to tip of maxilla; culmen sharply ridged, straight for basal half (more or less), then very gradually decurved until near end, where more strongly decurved, the tip of maxilla minutely but distinctly uncinate; maxillary tomium faintly concave, minutely notched subterminally; mandibular tomium very faintly convex, at least terminally, without trace of subterminal notch; gonys faintly convex basally, straight terminally. Nostril exposed, distinctly separated from feathering of latero-frontal antiæ, narrow, longitudinal (slit-like), overhung by a broad but not convex membraneous operculum. Rictal bristles distinct but rather few and slender; feathers of chin without terminal setæ. Wing rather large, with longest primaries extending slightly beyond secondaries, much rounded; fifth and sixth primaries longest, the tenth (outermost) less than half as long as the longest, the ninth very much shorter than, the eighth about equal to, secondaries. Tail slightly more than half as long as wing, rounded (graduation equal to much less than half the distance from nostril to tip of maxilla), the rectrices (10) rounded at tip. Tarsus very long (decidedly longer than whole culmen, nearly half as long as wing), slender, the acrotarsium faintly scutellate, the planta tarsi completely fused; middle toe, with claw, decidedly shorter than tarsus (equal to or slightly longer than exposed culmen); outer toe, with claw, reaching to about middle of subterminal phalanx of middle toe, the inner toe decidedly shorter; hallux much longer than inner toe (about as long as outer toe), much stouter; basal phalanx of middle toe wholly united to both lateral toes; claws moderate in size and curvature, that of the hallux much shorter than its digit. Plumage full, soft, and blended, that of rump and flanks elongated, more lax or fluffy; feathers of pileum not elongated.

Coloration. — Above plain brown; sides of head blackish and white, or tawny; beneath white passing into dusky on flanks and under tail- coverts, the chest crossed by a band of black (M. collaris) or under parts of body gray, chest streaked with black and white, and throat white bordered on each side by a black stripe; sexes alike.

Range. — Southwestern Costa Rica to Cayenne and Ecuadór. (Two species.)^[2]

MICROBATES CINEREIVENTRIS SEMITORQUATUS (Lawrence).

HALF-COLLARED ANTWREN.

Adults (sexes alike). — Pileum and hindneck plain warm-sepia brown; rest of upper parts plain sepia, the edges of greater wing- coverts and secondaries (especially the tertials) more rufescent, the rectrices decidedly darker terminally; sides of head (except lores) plain ochraceous-buff to deep tawny-buff, this color extending more or less over sides of neck; lores dull whitish broken by dusky bristle- like tips to feathers; anterior portion of malar region whitish; chin and throat white or grayish white, the latter bordered along each side by a broad but more or less broken streak of black; rest of under parts plain gray (no. 6 to mouse gray) passing into olive on flanks and under tail-coverts, the upper chest broadly streaked with black; maxilla brownish black with paler tomium, mandible dull whitish (horn color, flesh color, or straw yellowish in life); iris brown; legs and feet horn color (dark bluish gray in life).

Adult male. — Length (skins), 95-106 (100); wing, 51-57 (53.9); tail, 26.5-29.5 (27.7); culmen, 17.5-19 (18.1); tarsus, 22-24.5 (23.7); middle toe, 13-14.5 (13.6).^[3]

Adult female. — Length (skins), 92-101 (96); wing, 50.5-53.5 (51.5); tail, 24-28 (26.3); culmen, 17-19 (18.1); tarsus, 20.5-24.5 (23.1); middle toe, 12.5-13.5 (12.9).^[4]

Costa Rica (Jiménez; San Carlos; La Balsa; Rio Súcio; Pacuare; Guápiles; Guácimo; Cuábre; El Hogár; Carrillo; La Vijágua) and Panamá (Volcan de Chiriquí; Santiago de Verágua; Lion Hill; Panamá) ; Colombia (Antioquía) ?

Ramphocænus semitorquatus Lawrence, Ann. Lyc. Nat. Hist. N. Y., vii, 1862, 469 (Lion Hill Station, Panamá,; coll. G. N. Lawrence); ix, 1868, 108 ("Valza," i. e. La Balsa, Costa Rica; crit.). — Salvin, Proc. Zool. Soc. Lond., 1867, 145 (Santiago de Verágua, Panamá; crit.); 1870, 195 (Calovévora, Panamá). — Frantzius, Journ. für Orn., 1869, 305 (Costa Rica). — Boucard, Proc. Zool. Soc. Lond., 1878, 61 (San Carlos, Costa Rica). — Zeledón, Anal. Mus. Nac. Costa Rica, i, 1887, 115 (Rio Súcio, Costa Rica).

[Ramphocænus] semitorquatus Sclater and Salvin, Nom. Av. Neotr., 1873, 73.

Rhamphocænus semitorquatus Sclater, Ibis, 1883, 96 (Veragua, Panama; Antioquia, Colombia; crit.); Cat. Birds Brit. Mus., xv, 1890, 262 (Veragua; Antioquia). — Salvin and Godman, Biol. Centr.-Am., Aves, ii, 1892, 219 (La Balsa, Rio Sucio, and San Carlos, Costa Rica; Santiago de Veragua, Calovevora, and Lion Hill, Panama; Colombia). — Bangs, Proc. New Engl. Zool. Club, iii, 1902, 42 (Volcan de Chiriquí, Panama, 1,000-2,000 ft.). — Carriker, Ann. Carnegie Mus., vi, 1910, 612 (Caribbean lowlands to 1,500 ft., Costa Rica; habits).

[Rhamphocænus] semitorquatus Sharpe, Hand-list, iii, 1901, 28.

(?) Rhamphocænus cinereiveniris (not of Sclater?) Sclater and Salvin, Proc. Zool. Soc. Lond., 1879, 525 (Antioquia, Colombia; crit.).

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1. ?, parvus et ?, qui incedit." (Sclater and Salvin.)
2. I have not seen M. collaris (Pelzeln), the type of the genus, and the above generic description is drawn up from M. cinereiventris and its subspecies semitorquatus.
3. Thirteen specimens.
4. Ten specimens, from Costa Rica.

   Locality.	Wing.	Tail.	Culmen.	Tarsus.	Middle toe.
   males.
   Ten adult males from Costa Rica	53.9	27.6	18.1	23.7	13.6
   Two adult males from western Panamá (Chiriquí)	53.7	28.7	18.5	23	13
   One adult male from eastern Panamá (line of railway)	54	26.5	-	22.5	14