FAMILY TYRANNIDAE 529 



moving groups of small forest birds. It has been my impression that 

 such association has been temporary for only short periods, and in 

 limited movement in travel. 



The voice is a low, rattling call, toadlike in sound. The trachea is 

 much enlarged, the swelling beginning below the larynx, and ending 

 immediately above the syrinx. This development in size resembles 

 that found in Lophotriccus pileatus, but differs in Oncostoma by 

 being compressed from side to side. While most of the calls come 

 from males, they are given also by females, as I have determined 

 from collected specimens. On one occasion, at Charco del Toro, two 

 were calling persistently and chasing one another from perch to 

 perch ; both proved to be females. 



An early account of the nest of this species is that of D. E. Har- 

 rowes (Auk, 1936, pp. 336-337), of one found August 7, 1933, on 

 the Rio Indio trail near Gatun. It was in dense, low jungle about a 

 meter from the ground, "a small, flask-shaped structure . . . hung 

 from slender twigs. The entrance was a small, round hole in one 

 side near the top, with a 'roof projecting out and serving to shelter 

 it. . . . When discovered it contained one very small white egg . . . 

 with a very few minute spots of red-brown about the larger end." 

 Skutch (Pac. Coast Avif., no. 34, 1960, pp. 558-560) in late April 

 1935, on Barro Colorado Island, found a nest about 4 meters from 

 the ground, hung from a slender branch in a small tree in the forest 

 beside a little stream. It was about 140 mm long by 75 mm in 

 diameter, and had a narrow, round opening leading to the inner 

 chamber. It was "constructed almost wholly of very light-colored, 

 soft fibers . . . lined with soft, buff-colored down from some kind 

 of seed." On May 2 it held two white eggs "with a wreath of small 

 blotches and fine scrawls of pale brown around the thick end, and a 

 few such marks scattered elsewhere. . . . They measured 15.9x 

 12.7 and 15.9 X 12.3 millimeters." 



Beyond Panama, Oncostoma olivaceum ranges across northern 

 Colombia from the lower Rio Atrato, Choco, east in the middle 

 Magdalena region from western Santander north to the Santa Marta 

 area. Specimens from this area do not differ from the typical popula- 

 tion of Panama. 



LOPHOTRICCUS PILEATUS LUTEIVENTRIS Taczanowski: 

 Scale-crested Pygfmy-tyrant, Moscareta Cresta-Escamada 



[Lophotriccus squamicristatus] subsp. luteiventris Taczanowski, Orn. Perou, 



vol. 2, 1884, p. 231. (Chiriqui.) 

 Lophotriccus squamicristatus minor Cherrie, Proc. U.S. Nat. Mus., vol. 14, 



