286 BULLETIN 133, UNITED STATES NATIONAL MUSEUM 



jerking their tails continually. They have several soft mewing or 

 nasal notes, but do not become as excited at intrusion as do many 

 small birds. A male taken February 7 (preserved as a skeleton) 

 was in breeding condition and from the appearance of the ab- 

 domen had been engaged in incubation. 



THAMNOPHILUS GILVIGASTER DINELLII Berlepsch 



Thamnophilus dinellii Berlepsch, Bull. Brit. Orn. Club, vol. 16, May 28, 

 1906, p. 99. (Estancia Isca Yacu, Santiago del Estero, Argentina.)^'' 



The bird here treated has been known variously as maculatios, 

 caerulescens, and gilvigaster until dinellii was described by Berlepsch. 

 The present combination seems to have been made first by Hartert.^'' 



Of this form I collected the following skins : Resistencia, Chaco, 

 July 9, 1920, male and female; Las Palmas, Chaco, July 13, 14, 20, 

 21, and 30, two males and three females; Riacho Pilaga, Formosa, 

 August 8 and 11, two females; Tapia, Tucuman, April 12, 1921, 

 immature female. These differ from gilvigaster from Uruguay in 

 uniformly paler coloration on the ventral surface, Avith the grayish 

 wash of the breast lighter and less extensive. Birds from the Chaco 

 agree in general with the single skin from Tapia, Tucuman, though 

 this bird from Tucuman, and two from the Eiacho Pilaga. Formosa, 

 are slightly grayer on the dorsal surface than the series from the 

 Territory of Chaco. 



The present ant bird, in the Chaco, was common in dense under- 

 growth under heavy trees, but at times was found in more open 

 groves scattered over the savannas. In general it had the motions 

 of a titmouse, save that it did not cling to limbs, but with this 

 mannerism combined the jerking of the tail and twitching of the 

 wings of a flycatcher. It fed at times on the ground, where it hopped 

 slowly about, pausing to peer around, but more often worked through 

 limbs rising 3 or 4 meters from the ground. The birds had much 

 curiosity and were easily called out from the heavier coverts. Their 

 notes were somewhat varied, the usual one resembling pruh yruh 

 pruh-h, given in a mewing tone. In spring, males mounted into the 

 top of some bush or low tree where, concealed in the leaves, they 

 sang a pleasing whistled repetition of notes suggestive of the song 

 of the white-breasted nuthatch {Sitta carolinensis) . 



The Toba Indians called them Jcwo o likh. 



A male, shot July 9, had the maxilla and extreme tip of the 

 mandible black; base of mandible gray number 5, with an indis- 

 tinct, grayish line along the cutting edge ; tarsus and toes slate gray, 

 underside of toes yellowish ; iris dark brown. A female was similar 

 but had the colors somewhat duller. 



58 Hellmayr, Field Mus. Nat. Hist., Zool. ser., vol. 13, pt. 3, Nov. 20, 1924. p. 103, 

 states ttiat Berlepsch's type specimen comes from Santiago del Estero, though In the 

 original description it is listed from Tucuman. 



«' Nov. Zool.. vol. 16, 1909, p. 221. 



