272 Birds of Colorado 



of trees, whence it darts out after its insect prey. Some 

 controversy seems to have arisen in regard to the 

 situation of the nest : Aiken states, as is the case with 

 the eastern bird, it is usually saddled on the outer fork 

 of a horizontal bough, and in plain sight. It is somewhat 

 deeper and more strongly constructed than that of the 

 eastern bird, and is covered externally with leaves and 

 bark, not, as a rule, with lichens. Fresh eggs are to be 

 found at low elevations in the middle of June ; but at 

 Twin Lakes, Scott took a nest with three eggs on July 

 11th. These, generally three in number, are white 

 to pale cream, spotted and blotched with reddish. 

 They cannot be distinguished from those of the eastern 

 bird. 



Genus EMPIDONAX. 



Small Flycatchers — wings measuring from 2-25 to 3-25 — with broad, 

 flattened bills, the width of which across the nostrils is about equal 

 to the culmen ; wings long and pointed, the tenth (outer) primary 

 between the fourth and sixth, the ninth to seventh the longest ; tail 

 even or slightly emarginate, shorter than the wings, generally about 

 I to I ; legs and feet of normal size, the tarsus from | to ^ the 

 length of the wing, always exceeding the culmen and middle toe and 

 claw. 



About thirty species and subspecies have been recognized, spread 

 over the greater part of America, except the West Indies. Seven of 

 these have been taken in Colorado. 



The members of this genus have a very similar coloration, varying 

 from olive to dark grey above and from pale yellow to whitish-grey 

 below ; they are also very nearly of the same size, and are consequently 

 difficult to discriminate ; the following key, therefore, should be used 

 with caution, and the description in aU cases referred to before a 

 satisfactory conclusion can be reached. 



Key of the Species. 



A. Yellow wash of under-side richer, and distinctly extending over 



the throat ; size large (wing 2-85) ; tail emarginate. 



E. difficilis, p. 273. 



B. Yellow wash of under-side paler, not extending over the throat, 



which is markedly white. 



