162 University of California Publications in Zoology [Vol. 12 



willow seedlings some three hundred yards off. The inference was 

 that the males had selected the appropriate site for the location of 

 nests, but that pairing off had not yet occurred. Here, as with many 

 other birds of the Colorado Valley, it was evident that nesting time 

 is deferred until the period of highest water, which custom doubtless 

 obviates danger of destruction of nests through flooding. Elsewhere 

 in the Austral zone red-winged blackbirds are caring for broods of 

 young at so late a date as May 2. 



The species was common near Pilot Knob flying back and forth 

 overhead, evidently between breeding and feeding grounds somewhere 

 in the vicinity. Nowhere was it seen outside of the confines of the 

 river flood plain, so that the desert mesa forms the practical barrier 

 to its farther spread laterally. 



Thirty-three specimens were preserved, nos. 13009-13041. 



The red-winged blackbirds of the Colorado Valley show themselves 

 to be markedly different from those of the Pacific slope of southern 

 California. The latter are Agelaius phoeniceus neutralis Ridgway; the 

 former are here referred to Agelaius phoeniceus sonoriensis, following 

 Ridgway's last diagnosis (1902, p. 337). Although the type locality 

 of sonoriensis is stated by Ridgway (1902, p. 338) to be Mazatlan, 

 Arizona had previously been fixed as type locality by Nelson (1900, 

 p. 126), and the A. O. U. Check-List (1910, p. 233) further specifies 

 Camp Grant, Arizona. I have no Mexican material for comparison. 



The Colorado Valley form, as compared with neutralis, has the bill 

 in both sexes very much longer and slenderer. In some of the males 

 this feature is extraordinarily pronounced : the culmen. gonys and 

 lateral outlines are all concave, resulting in an acicular sharpness of 

 the bill. An opposite variation, however, leads to a moderately pointed 

 bill in six out of twenty-six males, which can be matched by picked 

 examples of neutralis. These u< iitnilis-Uke males are all but one 

 obviously immature. It is possible, of course, that some of these may 

 actually be transient or casual visitants of neutralis. But it appears 

 to me now as more likely that they are individual extremes of the 

 locally native form, which in the material at hand varies towards 

 them. 



The six females collected are all conspicuously different in colora- 

 tion, as well as in shape of bill, from neutralis. They have the colora- 

 tion ascribed to sonoriensis, the black streaking below being much nar- 

 rower and more distinctly contrasted against the extended white 

 ground ; also dorsally and on the sides of the head the pale edgings 



