152 University of California Publications in Zoology [Vol. 12 



Empidonax wrighti Baird 

 Wright Flycatcher 



In only one instance was the presence of this species ascertained, 

 and the specimen secured happened to be the first Empidonax taken : 

 no. 12873, male, shot from the upper branches of a willow in the then 

 leafless first-bottom timber, on the California side, five miles south 

 of Needles, February 19. 



In spite of the largely increased extent of material illustrating this 

 genus, the relative characters of Empidonax griseus, Empidonax 

 wrighti, and Empidonax hammondi remain somewhat subtle. It would 

 seem that wrighti, as I now recognize it, is much less common in the 

 southwest even as a transient than formerly supposed, since out of 

 the thirty-nine examples of the genus taken by our Colorado expedi- 

 tion but one is referable to wrighti. 



To show upon what characters I base the discrimination of the 

 wrighti example in the present case, a comparison with a picked 

 average specimen of hammondi and of griseus is here given. All are 

 males of apparently ecpial age and stage of plumage wear, this being 

 very slight. The color differences are minute: hammondi is slatiest, 

 griseus ashiest. wrighti intermediate; wrighti is greenest dorsally and 

 pectorally ; the outer web of outer tail-feather is distinctly white 

 nearly to its tip in griseus, grayish white in wrighti, and but slightly 

 paler than rest of feather in hammondi. The lower mandible is 

 entirely blackish brown externally, in hammondi, dull or lighter 

 brownish in wrighti, while in griseus it is blackish brown at tip and 

 abruptly straw yellow for its basal two-thirds, brightest along the 

 rami. 



COMPARATIVE MEASUREMENTS IN MILLIMETERS OF THREE CLOSELY 



RELATED SPECIES OF EMPIDONAX OCCURRING TOGETHER 



IN SPRING IN THE COLORADO VALLEY 



