FAMILY TYRANNIDAE 493 



a species of eastern United States and Canada, common in Panama 

 as a winter visitor. 



The food appears to be small insects, taken on the wing or seized 

 from leaves and twigs in active foraging. Only rarely have I observed 

 one resting quietly on a shaded perch in forest, in the manner usual 

 for most small flycatchers. 



Its calls are rather sharp chipping sounds, without great carrying 

 power, varied rarely with low warbling notes. All are heard so seldom 

 that the main impression from acquaintance with the species is that 

 of its almost incessant activity. 



In central Panama, Black-tailed Flycatchers were in breeding con- 

 dition by the beginning of April. Nesting may continue rather long, 

 as A. O. Gross (Wils. Bull., 1964, p. 251) recorded nests with eggs 

 on Barro Colorado Island in June, July, and as late as August 13, 

 1925. 



They do not associate in pairs, and nest-building and care of eggs 

 and young is the task of the female alone. The nests are irregularly 

 rounded masses, roughly ball-like in form, suspended from the tip 

 of a slender branch or vine, over some open space, frequently above 

 a small forest stream or other water. They are made of rootlets, 

 soft fibers, small bits of leaf and other vegetation, with loose ends 

 hanging irregularly down from the sides, so that the whole suggests 

 a mass of plant material caught and held at random rather than the 

 planned structure of a bird. The entrance to the cup that holds the 

 eggs is at one side beneath hanging material so that the bird in incuba- 

 tion, eggs, or young are hidden from above and the side. Two eggs 

 in a set collected by E. A. Goldman at Portobelo, Colon, June 1, 1911, 

 have the ground color uniform vinaceous-cinnamon, with a narrow 

 wreath of snuff brown around the larger end, and fine dots of this 

 darker color scattered over the surface. In form they are subelliptical 

 with measurements of 17.1x12.0 and 17.9x12.6 mm. Another set 

 of two, also from Goldman, taken at Matachin, Canal Zone, on the 

 left bank of the Rio Chagres opposite Gamboa (now submerged in 

 Gatun Lake), May 6, 1911, are similar in form, but have the base 

 somewhat paler, light vinaceous-cinnamon, so that the dark band 

 around the larger end is in greater contrast. One egg measures 

 17.4 X 12.1 mm. The other is broken. 



The species ranges from western Costa Rica (mainly in the south- 

 west) through Panama and across northern Colombia to the lower 

 Magdalena Valley. In a considerable series collected by Carriker in 

 Colombia some average faintly paler, but most appear too closely 



