GENUS EMPIDONAX 



It frequents the second growth. Noted in under- 

 growth on high part of Barro Colorado Island on 

 several occasions. 



Genus Empidonax 



The small plainly colored flycatchers of 

 this, genus are often exceedingly difficult to 

 identify even when one has the specimen in 

 hand. They much resemble those of the 

 genera Myiochanes and Rhynchocyclus in 

 appearance. They may be distinguished 

 from the former genus by their stouter, 

 broader-shouldered build, and by a habit of 

 frequently twitching the tail up and down. 

 They also habitually sit somewhat less up- 

 right, have a conspicuous eye-ring and their 

 under parts are less deeply shaded with olive 

 on the sides. From the species of Rhyn- 

 chocyclus, the much smaller head and nar- 

 rower, practically straight, bill of the present 

 genus serves as a distinguishing character. 

 In the north (the Canal Zone species are 

 migrants), they each have characteristic song 

 notes, but these are not likely to be heard in 

 the Canal Zone where they will usually be 

 found nearly or quite silent. 



If a bird is identified as an Empidonax, its 

 size (R. virescens, E. t. traillii and E. traillii 

 alnorum are 10 mm. or more longer than 

 the others), the size of the bill (E. minimus 

 has .a proportionately smaller bill than the 

 others), and the color of the under parts, 

 wing bars, etc., may give clues to the species 

 (see descriptions), but in the case of im- 

 mature specimens or those in poor plumage, 



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