250 NORTH AMERICAN FAUNA 61, FISH AND WILDLIFE SERVICE 



back, so characteristic of iliaca and almost absent in unalasch- 

 censis or insularis, is much subdued and clouded over by the 

 duskiness of the coloration. The spotting on the breast is slightly 

 bicolored, as in iliaca, but it is more like that in unalaschcensis. 

 Osgood (1904) evidently referred to one of these specimens, the 

 adult taken by Johnson, and described it as "intermediate in 

 character between iliaca and unalaschcensis, but nearer to iliaca." 

 Swarth (1920), in his revision of this genus, properly recog- 

 nized three fox sparrow groups, the iliaca group, the unalasch- 

 censis group, and the schistacea group. He considered all these 

 to be subspecifically related, but this relationship is complex, and 

 not entirely clear. In the same general area occupied by the 

 iliaca group, as mentioned above, there are typical specimens 

 of the unalaschcensis group. Osgood (1904) reported — 



One specimen was taken and several were seen in the mountains near Iliamna 

 Bay July 12; two others, one adult and one immature bird, were taken at 

 Iliamna Village July 14; and another young bird was taken on Lake Iliamna 

 at the Nogheling portage July 18. These agree well with birds from the 

 Shumagin Islands and localities to the westward on the Alaska Peninsula . . . 

 A specimen of typcial unalaschcensis in fresh fall plumage was taken at 

 Nushagak September 19; another, which is not quite typical, but easily 

 referable to unalaschcensis, was taken at the same locality by J. W. Johnson 

 October 22, 1884. 



The last two specimens just mentioned may have been fall 

 migrants, though they were north of the known breeding range, 

 rather than south of it. But omitting these as possible breeding 

 birds, there is hardly room for an area of intergradation between 

 the known breeding ranges of these two well-marked forms. As 

 Osgood suggested many years ago, there does not appear to be 

 gradual intergradation here. The intermediate specimens de- 

 scribed above show the abrupt mixtures found in hybrids. 



Apparently, altivagans is the form in which we may look for 

 complete intergradation with typical iliaca. Specimens of alti- 

 vagans available for this study did not show complete intergrada- 

 tion. Presumably this may take place somewhere in Alberta. 

 On the whole, on the basis of material that is available at pres- 

 ent, iliaca seems to be a species apart, although it may be proper 

 to assume intergradation with altivagans somewhere in Canadian 

 territory. Therefore, granting subspecific status, iliaca is an ex- 

 ample of a subspecies that intergrades with another subspecies 

 at one part of its range and becomes a species, with hybrids, 

 where it meets another subspecies of the same group, as at the 

 base of Alaska Peninsula. 



