1312 U.S. NATIONAL MUSEUM BULLETIN 23 7 part 3 



ture birds might be mistaken by a beginner for several other birds 

 with reddish brown on the crown. * * * When there are adults with 

 the immature birds, the resemblance in the pattern of the head mark- 

 ings is obvious." Hoffman mentions the rufous-crowned and chipping 

 sparrows as species with which immature white-crowned sparrows 

 could be confused. The rufous-crowned sparrow lacks the pale stripe 

 through the center of the crown, and the reddish crown of the chipping 

 sparrow is set off sharply from the sides of the head by a white or 

 whitish stripe and a black line below it." 



Although one can easily identify the species, one cannot always 

 distinguish between races of white-crowned sparrow on the basis of 

 morphological characters alone. With practice one can, however, 

 assign most individuals to one of two groups: nuttalli-pugetensis or 

 gambelii-oriantha-leucophrys. For adults, the differentiating charac- 

 ters are the hue of the feathers on back and rump and the color of the 

 bill. If an adult has brownish back and rump feathers and a yellowish 

 bill, it belongs to the nuttalli-pugetensis group. If it has back feathers 

 with reddish centers and grayish margins, grayish rump feathers and 

 a cinnamon brown or reddish bill, it belongs to the gambelii-oriantha- 

 leucophrys group. To distinguish between immatures of these two 

 groups, bill color, but not color of back or rump feathers, is a reliable 

 criterion. A different grouping, based on the color of the lores in the 

 adult, places those with white or grayish lores in one group (nuttalli, 

 pugetensis and gambelii) and those with a black lores (oriantha and 

 leucophrys) in another. This distinction does not hold in all cases, 

 however. Walter E. C. Todd (1953) reports "white-browed indi- 

 viduals" from the offshore islands and mainland of Hudson and James 

 Bays in the midst of the leucophrys breeding range. 



To distinguish between the races within each group is still more dif- 

 ficult. Nuttalli and pugetensis cannot be told apart by morphological 

 characters alone. So similar are the members of these two races that 

 separation requires comparison with large series of study skins, and 

 then only the individuals at the extremes of the range of variation 

 can be identified with certainty. Song pattern, on the other hand, is 

 a reliable criterion for distinguishing between the two races. In lo- 

 calities where both winter together, the best way to distinguish the 

 song patterns is to follow the advice of Peterson (1941) and "learn 

 the song pattern of the local breeding birds thoroughly, and when the 

 migrants * * * arrive * * * proceed to memorize carefully their respective 

 song patterns." In the San Francisco Bay Region this system works 

 particularly well, for the local populations of NuttalFs sparrows sing 

 short simple songs quite different from the longer and more em- 

 bellished ones of wintering pugetensis. At Carmel and Guadalupe, 

 Calif, the distinction is more difficult to make, for the Nuttall's 



