374 BULLETIN 197, UNITED STATES NATIONAL MUSEUM 



the warbling vireo was one of the common species, widespread wherever there 

 were deciduous trees. It was of regular occurrence in the groves of aspens and 

 cottonwoods. The favorite habitat was in trees 25 to 30 feet high where 

 there was some undergrowth and leaf litter. But the birds kept closely within 

 the crown foliage. This was the most numerous species in the birches and willows 

 which lined the streams. It occurred also, but less commonly, over the ridges 

 in mountain mahoganies. Chokecherry thickets provided suitable homes, es- 

 pecially when in fruit in the fall. Individuals were seen a few times in piJQons. 

 * * * One was singing in bushes of Symphoricarpos on an east-facing ridge 

 at 8600 feet near Kingston Creek. The nearest trees were mountain mahogany, 

 200 to 300 yards distant. 



Spring. — ^The western warbling vireo evidently occurs mainly as a 

 migrant, in Guatemala, for Ned Dearborn (1907) says : "One was taken 

 and another seen at El Eanclio January 6th. No more were seen until 

 March 24th, when they were found at Patulul in abundance, and so 

 continued, at least, until April 2d. Seven were collected at Patulul. 

 At this time, they were passing through the trees in loose flocks and 

 were evidently migrating. The March and April specimens were 

 undergoing a scattered moult, not a general renewal, on head and 

 breast." 



Mr. Cogswell says in his notes: "During the spring migration in 

 April and early in May, warbling vireos are quite common throughout 

 Pasadena, Calif., especially sections with oaks and sycamores. Many 

 migrants sing constantly during their stay of a few hours or a day or 

 so in one vicinity." 



Mr. Kathbun (MS.) says of the spring migration in western Wash- 

 ington : "At first a few in company will be seen, these little birds seem- 

 ing to pass on. Often a day or two elapses before any more are seen ; 

 then once more a few pass by. This is followed by the appearance of 

 numbers of the vireos, after which the species is common and will be 

 found in its accustomed places. This movement seems to be covered 

 by a period of about 15 days." 



Nesting. — Mr. Rathbun tells me that he finds the nests of the west- 

 ern warbling vireo in maples, alders, and other deciduous trees from 

 4 to 40 feet above ground, "but, as a rule, one can expect to find them at 

 some considerable height." He gives me this good description of a 

 nest : "This nest was attached in the usual way to a fork of one of the 

 branches of a young alder tree, which grew at the edge of a clump of the 

 same kind of growth, the nest being suspended only six feet above the 

 ground. Its construction represented the ordinary cup-shaped nest 

 made by most vireos, and the materials used were similar except in one 

 marked respect; the outside of this nest was almost entirely of the 

 dingy-gray, cottony substance from the black cotton wood tree, this 

 material held in place by means of long blades of green grass; and 

 there was also tied on the outer side a green alder leaf. Some of the 

 blades of grass completely encircled the nest, aiding its attachment 



