FAMILY TYRANNIDAE 5O3 



tail 21.0-25.5 {22,7) culmen from base 11.2-13.3 (12.3), tarsus 

 13.5-14.9 (14.0) mm. 



Females (10 from Pacific slope of Veraguas, Province of Panama, 

 Darien, and San Bias), wing 49.4-53.9 (51.3). tail 19.2-22.8 (20.8), 

 culmen from base 11.7-12.9 (12.3, average of 9), tarsus 12.7-14.4 

 ( 13.5, average of 9) mm. 



Resident. Locally fairly common in forested areas in the Tropical 

 Zone from the Canal Zone eastward through Darien and San Bias 

 (to Puerto Obaldia) ; recorded in lesser numbers through western 

 Panama (Santa Fe, Bugaba) to the Costa Rican boundary; to 850 

 meters on Cerro Campana. and 900 meters on Cerro Pirre. 



These birds are small in size but heavy in body, the relatively 

 large wings and abbreviated tail presenting an unusual outline as the 

 bird rests on a low branch near the ground, erect in usual flycatcher 

 pose. The short, broad bill may be visible in outline as they turn the 

 head. In active movements, when they may cling momentarily to 

 the side of an upright stem, they may suggest an ant-shrike. Usually 

 they are encountered singly, or in pairs, rarely, with scattered compa- 

 nies of other forest birds. And more rarely, among the birds captur- 

 ing insects over raiding ant swarms. Normal haunts are swampy 

 woodlands, or elsewhere low down near the ground in heavily shaded 

 forest. The usual call is a chirping sound, suggesting that of some 

 insect. This may be varied by a low trill, a common song in the 

 forests that they frequent, but one with slight carrying power, heard 

 only when the bird is near. As they move about the wings may be 

 fluttered occasionally. 



The oil gland in these birds, for their size, seemed unusually large. 

 In a female taken at the mouth of the Rio Paya, February 15, 1959, 

 the transverse diameter across the lobes was 15 mm. 



Skutch (Pac. Coast Avif. no. 34, 1960, pp. 332-339) describes a 

 display, apparently unique among flycatchers, in which the bird in 

 flight produces with its wings "a peculiar sound somewhat like 

 that . . . made by twanging a tightly stretched rubber band." Car- 

 riker (Ann. Carnegie Mus., vol. 6, 1910, p. 729) described the nest, 

 seen in Costa Rica, as a well- formed cup placed from 1 to 2 meters 

 above the ground in a small upright fork made of "fine bark fibres, 

 moss, and rootlets, and lined with coarse, black hair-like fibres of one 

 of the common ferns. A tuft of fibres of irregular length trailed 

 from the bottom, and the outer walls were slightly decorated with 

 lichens and spider-webs." Skutch found that the female alone built 

 the nest and incubated the eggs, but that the male aided in feeding 



