DISTRIBUTION OF THE BLUE-HEADED GREENLET 509 



is largely replaced by V. plumbeus in the breeding season, and 

 even in 1874 I was obliged, according to the knowledge we 

 then possessed, to except the region in question from the habitat 

 of the bird, as was also done the same year by the authors of 

 the " History of North American Birds 77 . We now know, how- 

 ever, the exception was unnecessary, the apparent absence of the 

 species from the Colorado Valley being occasioned by the fact 

 that there it is rather a migrant than a breeder, and that V. 

 plumbeus is conspicuous in the breeding season in this region. 

 Mr. Henshaw's observations may be cited in support of these 

 statements : 



" The Solitary Vireo appears to occur in the Southern Rocky 

 Mountains only as a migrant, and to be wholly replaced there in 

 summer by the nearly allied variety, the Plumbeous Vireo (var. 

 plumbeus). In its course southward from its northern breeding 

 ground, it appears to follow the mountain ranges, and to con- 

 fine itself to the pine region. During the latter part of Septem- 

 ber I found the species occurring quite numerously at Mount 

 Graham, where it was seen only among the lofty pines, usually 

 accompanying other birds, as the Audubon's Warbler and Xut- 

 hatches. It could scarcely be said to be in song ; yet, as it 

 moved about from branch to branch, it occasionally paused to 

 give utterance to a few strains, which, though broken and 

 detached, were sufficient to bring to mind the beautiful melody 

 to be heard from this bird in the vernal season in variety 

 and richness of notes not surpassed by the song of any of the 

 family." 



Mr. Ridgway's recent paragraph is to like effect : " This spe- 

 cies was met with only during its autumnal migrations, when it 

 seemed to be not uncommon in the month of September among 

 the canon thickets of the western slope of the Clover Mountains. 

 A single specimen was also shot in a buffalo-berry thicket 

 in Buena Vista Canon, on the eastern slope of the West Hum- 

 boldt Mountains in September of the preceding year. It is 

 still a question whether such individuals of this species were 

 migrants from the higher portions of the mountains, or from a 

 more northern region ; but that their migration was not vertical 

 is most probable." This seems to be a judicious query ; for, 

 though we cannot yet affirm that the Solitary Vireo actually 

 breeds in the Colorado Valley, we may remember that the evi- 

 dence against it is unly negative 5 and I infer, from our general 

 knowledge of the fauna of this region, that the bird will evi- 



