724 U.S. NATIONAL MUSEUM BULLETIN 23 7 part 2 



little musical quality, the song is delivered with visible effort as 

 though it had to be squeezed out. 



Distribution 



Range, — Baja California, California, and northwestern Sonora. 



Breeding range. — The large-billed Savannah sparrow breeds in 

 northeastern Baja California (delta of the Colorado River, San Felipe) 

 and northwestern Sonora (mouth of Colorado River south to Isla 

 Patos, intergrading with P. s. atratus). 



Nonhreeding range. — Ranges in nonbreeding seasons from central 

 coastal and southern California (Morro Bay, San Miguel Island, San 

 Clemente Island, San Diego, Mecca, rarely from Santa Cruz) south 

 along both shores of Baja California to the Cape district, to islands 

 of the Gulf of California, the Sonoran coast, and northern Sinaloa 

 (to lat. 25° N.). 



Egg date. — Baja California: 1 record, April 6. 



PASSERCULUS SANDWICHENSIS ATRATUS van Rossem 



Sonora Savannah Sparrow 

 Contributed by Wendell Taber 



Habits 



This most southerly member of the rostratus group is found in the 

 tidal marshes of the coast of central and southern Sonora at least to 

 the Sonora-Sinaloa boundary. The winter range is imperfectly 

 known, although some individuals occur at various points in the 

 breeding range at that season. It is found also, perhaps only casually, 

 in the Cape region of Baja California. 



Van Rossem (1947) states that it is similar in size and proportion 

 to rostratus but averages slightly larger in aU dimensions. Coloration 

 grayer and much darker, the central streaking on dorsal feathers 

 fuscous black; ventral streaking wider and black rather than brown, 

 reddish, or gray. He also says that although specimens from the 

 northern part of the range show marked approach to rostratus, there 

 seems to be relatively little variation in atratus. However, there 

 is the same marked sexual difference seen in rostratus in the character 

 of the interscapular streaking, the pattern of which is much more 

 sharply defined and less diffuse in females than in males. 



Distribution 



Range. — The Sonora Savannah sparrow is resident in coastal 

 marshes from central Sonora (Tepopa and Kino bays) south to cen- 



