466 BIRDS OF THE REPUBLIC OF PANAMA PART 3 



Colorado Island, September 6, 1960, Willis) and remain to late April 

 or early May (Barro Colorado Island, May 1, 1961, Willis). The 

 record for Isla Taboguilla is of one taken March 18, 1952. 



The Acadian Flycatcher is widely distributed, found through un- 

 dergrowth and the lower limbs in more open forest, coming also to 

 thickets along the borders of fields and pastures. In the main it 

 ranges under leaf cover, perching on small branches from which it 

 sallies to capture flying insects or, less often, to seize those moving 

 over twigs and leaves. The prey is small and covers a wide variety 

 of species. Small berries are eaten also, but seem to form only a 

 minor part of the winter food. The birds range singly as scattered 

 individuals, though in October and March, two or three may be found 

 in the same area, but not closely associated. Willis (Living Bird, 

 1966, pp. 193-195) in observations on Barro Colorado Island found 

 them associated with moving ant swarms with some regularity. They 

 call occasionally, usually a single explosive note, accompanied by a 

 twitch of the tail. On the whole, they live in these tropical forests 

 much as they do on their northern nesting grounds. 



Two-thirds of the specimens in the considerable series in the Na- 

 tional Museum from Panama and Colombia, collected over a period 

 of 60 years, are females, which suggests a separation of the sexes in 

 their migrations. Traylor (Auk, 1968, p. 691) found that all, im- 

 mature and adult, have a complete molt between December and April 

 when in their winter range. 



The birds vary considerably in the amount of yellow on the under 

 surface so that the brighter ones suggest Empidonax flaviventris. 

 W^iile in life there may be confusion between them, in comparison 

 of specimens the present species differs in being paler yellow on the 

 abdomen, with the chest band lighter gray. The wing, tail, and bill 

 in virescens also are slightly longer. 



EMPIDONAX ATRICEPS Salvin: Black-capped Flycatcher, 

 Moscareta Gorranegra 



Empidonax atriceps Salvin, Proc. Zool. Soc. London, March 24 (:=November) 

 1870, p. 198. (Volcan de Chiriqui, Panama.) 



Small, slender ; above, olive-brown with crown black ; tail relatively 

 long, distinctly notched at tip ; nostril completely exposed. 



Description. — Length 105-115 mm. Adult (sexes alike), crown 

 and hindneck blackish brown ; back, scapulars, and rump olive to 

 olive-brown ; upper tail coverts darker ; wings dull black ; greater and 



