212 University of Calif orma Publications in Zoology TTol. 24 



a distance. At Glenora, July 1, an extremely dark individual was seen, 

 the body almost black ; this again was identified by means of the char- 

 acteristic tail color. Others were observed at Doch-da-on Creek, during 

 July. 



All the birds of this species seen thus far had been either in the 

 dark phase or else were light breasted birds that were not notably 

 light colored otherwise. Then, at Flood Glacier, a family of extremely 

 light colored individuals was encountered. On July 26, and on sub- 

 sequent days, an adult red-tail was several times seen from our camp, 

 sometimes perched in a tall spruce, sometimes flying past. The breast 

 and belly of this bird appeared to be gleaming white, and the back 

 seemed to have much white spotting. 



On July 31 Dixon found this adult feeding two full-grown young 

 ones in an opening in the forest ; though the parent was too wary to 

 be captured, he took both the immatures. These, like the old one, are 

 extremely light colored. Chin, throat and breast are continuously 

 white, the breast with a huffy suffusion, and the lower abdomen and 

 lower tail coverts are white. In the spotted tract across the middle of 

 the body below, and on the flanks, the dark spots are relatively small 

 and separated by wide areas of white. The area immediately sur- 

 rounding the eye, and between eye and bill, is white. In the feathers 

 on the top of head and back of neck are small central spots of black 

 or dusky, and extensive basal and marginal areas of white. Over the 

 entire upperparts the feathers are extensively white spotted and with 

 broad margins of white or pale buffy. 



In a large series of young calurus from various parts of the western 

 United States we have nothing at all like these birds. An immature 

 male borealis from Wisconsin is like the Stikine River specimens in the 

 uniformly white chin, throat, and breast, and in the restriction of the 

 black spots below, but it is not so white on the head and upperparts. 

 Buteo borealis krideri has been recorded from Alaska on the basis of 

 a light colored bird taken at Eagle during the winter of 1903 (B. H. 

 Bailey, 1916, p. 321). The red-tails, however, form a puzzling aggre- 

 gation of geographical races and color phases, and it does not simplify 

 matters in this case to assign to the subspecies krideri a range covering 

 part of the habitat of calurus. The present writer is disinclined to 

 regard the light colored birds just described as examples of krideri, 

 thereby extending the range of that form far to the westward. Most 

 of the red-tails seen throughout the Stikine region were of the recog- 

 nized calurus type. Until the meaning of the diverse phases of 



