April, 1919] Subspecies of Passerculiis Rostratiis 345 



has resulted in some interesting and rather unexpected dis- 

 coveries, which seem sufficiently important to present in print. 

 Among these results are some necessary changes in the nomen- 

 clature and systematic status of the races of this species. 



It may be worth while here also to emphasize the peculiar 

 distribution of Passerculiis rostratus and its forms. For birds 

 so well subspecilically differentiated, the large-billed sparrow 

 as a species occupies during the breeding season a relatively 

 small geographic area, extending only from the delta of the 

 Colorado River to central western Lower California; and all its 

 subspecies breed, so far as known, in isolated and exceedingly 

 restricted localities. They are, however, numerous there in indi- 

 viduals, as is evident both from the numbers observed in summer 

 and their abundance at various and widely separated places in 

 winter. The most astonishing feature of their life history is 

 the curious migration of at least two of the subspecies, knowledge 

 of which, however. Dr. Joseph Grinnell* and others have already 

 forecasted. In short, both Passerculiis rostratus rostratus and 

 Passerculus rostratus guttatus travel regularly far to the north 

 or northwest of their breeding range to pass the winter; and 

 at the same time other individuals of each form take, for the 

 same purpose, a long southward or southwCvStward journey. 

 This migration is almost, if not quite, unique, for at least no 

 other North American passerine bird follows even similar 

 routes. Herons and some other birds, as is well known, wander 

 northward and in other directions after the breeding season, 

 but not usually for the purpose of wintering ; and we know of no 

 other bird that regularly migrates both north and south from 

 its breeding ground to pass the winter months. The data on 

 which the above conclusions are based, together with the 

 elaboration of the biological phases of this problem, and the 

 discussion of the nomenclatural and other points involved, 

 will be found in the following pages under the different sub- 

 specific headings. 



* Auk, XXII, No. 1, January, 1905, pp. 16-21; and Pacific Coast Avifauna, 

 No. 11, October 21, 1915, p. 115. 



