302 BULLETIN 203, UNITED STATES NATIONAL MUSEUM 



hour and more than 14,000 in the 94 hours of observation." Accord- 

 ing to Albert K. Brand (1938), the approximate mean number of 

 vibrations per second in the song is 6,025, in the highest note 6,750 

 and in the lowest note 5,125. This comp)ares with a mean of 8,900 

 for the black-polled warbler, which is the shrillest passerine bird song. 



Field marks. — The conspicuous, bright yellow cheeks, the olive- 

 green back, the prominent black throat, the two white wing bands, and 

 the white outer webs of the lateral tail feathers will distinguish the 

 male in breeding plumage. The female is duller and has less black, or 

 none at all, on the throat. Young birds in the fall are much like the 

 female. See the descriptions under Plumages. 



Fall. — The fall migration of the black-throated green warbler 

 begins during the latter part of August, continuing through Sep- 

 tember and often through much of October. It seems to be a reversal 

 of the route followed in the spring. Similar haunts are frequented 

 in the fall in the company of vast congregations of other species. A 

 remarkable flight of various species of warblers was seen by Rev. W. F. 

 Henninger in Scioto County, Ohio, an account of which is quoted by 

 W.L.Dawson (1903) as follows: 



On September 28, 1899, I ran into a company of warblers which I would place 

 conservatively at two thousand individuals. It was like a regular army as it 

 moved up a long sloping hillside, and with wonderful rapidity. The wind was 

 blowing almost a gale from the north, and the birds allowed themselves to be 

 urged before it in the direction of their ultimate retreat, like half-stubborn 

 autumn leaves. Lisping, chipping, whirling, driving, they hurried on and I after 

 at full speed, panting, and wishing devoutly for a better chance to identify the 

 fleeing forms. Arrived at the top of the hill the army suddenly halted and 

 when I arrived breathless I had time to note the arrangement by species, not 

 rigid indeed, but sufliciently striking to command attention. In the center were 

 seen Hooded Warblers and a sprinkling of Chestnut-sides. On either side of 

 these in turn were Black-throated Greens and Sycamores, about two hundred of 

 each ; while the wings proper were held by Bay-breasts and Black-polls in enor- 

 mous numbers. * * * As the birds deployed to feed the specific lines were 

 not quite obliterated. 



Winter. — The following notes are contributed by Dr. Alexander F. 

 Skutch: "The black-throated green w^arbler is an abundant winter 

 resident in the Central American mountains, where it is well distrib- 

 uted on both the Caribbean and Pacific slopes. In Guatemala, it win- 

 ters from 1,000 to about 8,500 feet above sea-level, but is not abundant 

 at either of these extremes of altitude. Farther south, in Costa Rica, 

 it prefers slightly higher elevations. Here I have not recorded it be- 

 tween 2,000 and 2,900 feet, although the greater part of my bird- 

 watching in the country has been done in this altitudinal belt. From 

 2,900 feet, where it is rare as a winter resident, it ranges up to nearly 

 10,000 feet. At this elevation, I found it abundant on the Volcan 

 Irazu in late November. Less sociable than the Townsend warbler, 



