DISTRIBUTION OF AUDUBON's WARBLER 275 



try generally at corresponding latitudes in the Pacific water- 

 sheds, are witness of the birds through the winter. In such lat- 

 itudes, the species, as a species, is resident ; but it by no means 

 follows that the individuals which we see there in the winter 

 are those that were bred in the vicinity. In the nature of the 

 case, the question is not likely to be decided ; but the probabil- 

 ity is, to judge from analogy, that the winter representatives 

 of the species in New Mexico, Arizona, and Southern California 

 consist mainly of Northern-born birds which have migrated 

 southward, and that Mexico and Guatemala are supplied from 

 more southerly broods, that may have been raised in the very 

 latitudes where others of the species pass the winter. Should 

 such be the case, we see clearly that the migratory impulse is 

 carried out in all cases, even though Audubon's Warblers may 

 be found in certain areas at all seasons of the year. I think, 

 however, that we are all unconsciously apt to be biassed 

 respecting the general subject of the migrations of birds, by too 

 close reliance upon the north-south lines of movement, to the 

 extent of underrating the lateral and the up-and-down ranges 

 of species, which are particularly noticeable in countries much 

 diversified by mountains. For instance, the Black Snowbird is 

 commonly supposed to come from the North in the fall, and so 

 it certainly does ; but its sudden appearances, dependent upon 

 changes of the weather, remained unaccountable till it was 

 learned that the bird breeds in the mountains even as far south 

 as Virginia and North Carolina, and flies up and down, accord- 

 ing to exigencies of the weather. 



The general statements I have made respecting the move- 

 ments of Audubon's Warbler are gathered from sources too 

 numerous to be spread in full upon this record ; but I shall re- 

 coimt some of the more prominent observations which are at 

 our service. In Colorado State, according to Mr. T. M. Trippe, 

 Audubon's Warbler is abundant, migratory, and breeds from 

 an altitude of 9,000 or 9,500 feet up to timber-line. It reaches 

 Idaho from the South about the middle of May, goes higher up 

 to breed, and rears its young during the latter part of June and 

 in July, in the dense spruce forests of the mountain-sides, 

 whence it begins to descend in August, becomes common in 

 the lower parts of the country in September, and disappears by 

 October. In the same State, Mr. Aiken says this Warbler is a 

 common summer resident, particularly numerous during the 

 migrations, when it is dispersed over the whole country from 



