l86 BIRDS OF THE REPUBLIC OF PANAMA PART 4 



17 days and the young hatched without any natal down. Pin feathers 

 pushed through the skin when the nestlings were 2 days old, and at 7 or 

 8 days they were all feathered. The young were fed small insects and 

 spiders; they left the nest when 12 days old and able to fly only a few 

 yards. 



F. O. Chapelle (in litt. to Eisenmann) reports that in the Canal Zone 

 he regularly found it with wandering bird bands (consisting chiefly of 

 Formicariidae) conspicuous because of its musical trill, which is ac- 

 companied by tail vibration and sometimes by bill fluttering. The trill 

 is usually preceded and sometimes terminated by a low chip. When 

 foraging, the bird gives a drier, less musical version of the trill. 



Although Aldrich and Bole (Scient. Pub. Cleveland Mus. Nat. Hist., 

 1937, vol. 7, 1937, p. 116) considered -the birds they collected in 

 the western Azuero Peninsula to be almost identical to R. m. sanctae- 

 marthae of Colombia, this race is actually paler and browner than are 

 any Panamanian birds, all of which are referable to rufiventris. Speci- 

 mens in the Smithsonian show the range of rufiventris to extend into 

 Colombia in the departments of Choco, Antioquia, and Cordoba (So- 

 corre, Rio Sinu, and Quebrada Salvajin, Rio Esmeralda), whereas 

 birds from farther north in Cordoba (Pueblo Nuevo, 14.4 km north 

 of Planeta Rica; Nazaret, 19.2 km northwest of Tierra Alta) and east- 

 ward through Bolivar, Magdalena, and Norte de Santander (Guama- 

 lito, 7 km west of El Carmen) are referable to sanctaemarthae, the 

 range of which is thus rather far removed from Panama, particularly 

 the Azuero Peninsula. Some birds from the more westerly portions of 

 Panama tend to have less rufous on the head than, for example, those 

 from Darien, but these are darker and grayer on the dorsum than 

 sanctaemarthae and should be referred to rufiventris. Van Tyne and 

 Trautman (Occ. Papers Mus. Zool. Univ. Michigan, no. 439, 1941, 

 p. 9) comment on the frequently remarked color variation in Middle 

 American populations of this species. 



MICROBATES CINEREIVENTRIS (Sclater): Tawny-faced Gnatwren, 

 Cazajejen Carileonado 



Small, with long bill and short tail; upper surface brown; undersur- 

 face gray with throat white. 



Description. — Length 94-102 mm. Adult (sexes alike), crown dark 

 brown, back slightly lighter; wing coverts, primaries, and secondaries 

 dark brown, edged rufous; tail dark brown, tipped blackish; side of 

 face tawny; throat white, bordered by narrow black stripe on each side; 

 upper breast striped black and white; rest of undersurface gray with 



