FAMILY TYRANNIDAE 475 



Jr., in Colombia there are two, male and female, taken at Socarre 

 on the upper Rio Sinu, Department of Cordoba, April 12, 1949; and 

 two, also male and female, at Simiti, Department of Bolivar, April 2 

 and 12, 1947. Another male April 21, 1952, came from San Agustin, 

 Department of Huila, far to the south near the head of the Rio 

 Magdalena. These are assumed to have been collected on or near 

 their wintering grounds. It is not certain that this species winters in 

 Panama, as the records for April, from Isla Saboga and eastern 

 Darien, may be of birds that were in transit from a more southern 

 wintering ground. 



While long considered a subspecies of Empidonax traillii, it has 

 been shown recently, especially from studies originated by R. C. Stein, 

 that alnorum is marked by its characteristic three-noted song, usually 

 written fee-bee-o, while in the traillii group this is of two syllables, 

 jitz-bew. 



Gorski, (xA.uk, 1971, pp. 429-431) near Iquitos, Peru, from 

 October 31 to November 3, 1968, recorded regular response to play- 

 back of the three-syllabled call, but from this had no reaction to the 

 two-syllabled song, fitc-bezv of nominate traillii, an indication of a 

 South American winter home for the alnorum population. 



Where the nesting areas of alnorum and traillii join, as in northern 

 New York and southern New England, the two may be found to- 

 gether, but living as separate entities that are not known to hybridize. 

 From this the two are treated as separate species. The A.O.U. 

 Committee on Classification and Nomenclature suggests that where 

 specific identification between the two is not made, the group term 

 "Traill's Flycatcher" be used. 



In this present study, identification of specimens from Panama has 

 been made through details of dorsal coloration. Differences in com- 

 parative length of the fifth primary may be useful in separating indi- 

 viduals on the northern nesting grounds. But this may not be certain 

 in those from Panama where the outer primaries, even in April, may 

 not have attained their full growth, since these birds have their 

 complete annual molt while in the south. 



EMPIDONAX TRAILLII (Audubon) : Traill's Flycatcher, 

 Moscareta Aceitunada 



Small. In general like E. alnorum, but browner or grayer, less 

 greenish, above. 



Description. — Length 125-140 mm. Varying from olive-brown to 

 grayish brown and grayish above, separated in races through differ- 



