84 BULLETIN 203, UNITED STATES NATIONAL MUSEUM 



within the period. In one instance, a bird was observed to sing while 

 on the wing, repeating the song twice in the course of a short flight." 

 Albert R. Brand (1938) found the pitch of the Tennessee warbler's 

 song to be well above the average, the approximate mean count being 

 6,600 vibrations per second, the highest note about 9,150 and the lowest 

 4,025; this compares with an approximate mean of 8,900 vibrations 

 per second for the black-poll warbler, and about 4,000 for the average 

 passerine song. 



Field marks. — The Tennessee warbler has no prominent wing-bars 

 and no very conspicuous field marks. It might be mistaken for one of 

 the small vireos, but its bill is much more slender and acute. The male 

 has a gray crown, a light line over the eye, and a dusky line through 

 it ; the upper parts are bright olive-green and the under parts grayish 

 white. The female has a greener crown and more yellowish under 

 parts. For more details, see the descriptions of plumages. 



Fall. — The fall migration starts early in August, but is quite pro- 

 longed, many birds lingering in the northern States until early in 

 October and in the southern States all through that month. During 

 some seasons and at certain places the Tennessee warbler is exceed- 

 ingly abundant, sometimes far outnumbering any other species, but 

 it is very variable in its abundance. 



Mr. Trautman (1940) says that at Buckeye Lake, Ohio, "during 

 some years not more than 20 individuals could be recorded in a day 

 in the southward migration, nor more than a 100 in the season. In 

 other years the bird rivaled the Myrtle Warbler in numbers, and as 

 many as 1,000 individuals could be seen in a day and several thousands 

 during a migration. * * * Throughout the southward migration 

 the species did not confine itself to the upper sections of the taller 

 trees as in spring, but was found in almost equal numbers in smaller 

 trees and brushy thickets, in bushes and saplings along fence rows, 

 and in weedy fields." 



Professor Cooke (1904) says of the fall migration route : "The prin- 

 cipal line of migration is from the Mississippi Valley across the Gulf 

 of Mexico to Mexico and Central America. The eastern part of this 

 route probably extends from the southern end of the Alleghenies 

 across northwestern Florida to the coast of Yucatan and Honduras." 

 A. H. Howell (1932), however, gives several records for central and 

 southern Florida, and says : "In autumn, Weston reports a large mi- 

 gration on October 26 and 27, 1925, when 31 birds were killed at the 

 lighthouse near Pensacola on the two nights, and large numbers seen 

 on the morning of October 26 in vacant lots in the city." 



Dickey and van Rossem (1938) say of the migration in El Salvador : 



Dui-ing the fall migration of 1925, Tennessee warblers arrived in the vicinity 

 of Divisadero on October 13. No advance guard, that is, individuals arriving 



