304 BULLETIN 2 03, UNITED STATES NATIONAL MUSEUM 



early in the year from districts on the Pacific slope where they were 

 present during the wetter closing months of the preceding year. Thus, 

 on the Sierra de Tecpan I met none between December 7 and April 

 20, when the northward movement was in progress, and the birds seen 

 were doubtless transients rather than winter residents. And in the 

 higher parts of the Basin of El General in southern Costa Rica I have 

 recorded the species only in October, November, and December, after 

 which the nearly rainless season begins. But in the wetter climate of 

 Vara Blanca, they were seen throughout February and March until 

 their northward departure in April. 



"The black-throated green warbler withdraws from Costa Rica 

 about the middle of April, and by the end of the first week of May has 

 vanished from Guatemala. 



"Early dates of fall arrival in Central America are : Guatemala — 

 passim (Griscom), October 15; Sierra de Tecpan, August 9, 1933; 

 Finca Moca, October 29, 1934. Honduras— Tela, October 26, 1930. 

 Costa Rica — Vara Blanca, September 28, 1937; San Jose (Under- 

 wood), October 16; Basin of El General, October 22, 1936. 



"Late dates of spring departure from Central America are : Costa 

 Rica — Juan Viiias (Carriker), April 17; Vara Blanca, April 14, 1938. 

 Guatemala — passim (Griscom), May 4; Sierra de Tecpan, May 6, 

 1933. 



The following account of its winter haunts in El Salvador by 

 Dickey and van Rossem (1938) is also interesting: 



All through the mountainous districts, both in the interior and coastwise, the 

 blacli-throated green warbler is an extremely common winter visitant ; in fact, 

 it constitutes, at levels between 3,500 and 5,000 feet, fully 90 per cent of the 

 nonresident warbler population. The numerous flocks of from a dozen to half 

 a hundred individuals invariably formed the nuclei about which gathered 

 smaller numbers of other insectivorous species resident and nonresident. The 

 black-throated green warbler showed decided preference for the oak and pine 

 association at the altitudes mentioned, although it was by no means confined to 

 such environments. 



Many were seen in the coffee cover down to 3,000 feet on Mt. Cacaguatique 

 and 2,300 feet at San Salvador. A few birds reach as high as 8,000 feet, at 

 which level they were found in both pines and cloud forest on Los Esesmiles. 

 * * * The average winter range of virens lies approximately 3,000 feet below 

 that of toii^isc7idi, although strays and vagrants make the extremes of altitude 

 nearly the same in both cases. 



DISTRIBUTION 



Range. — Eastern North America from southern Canada to Panama. 



Breeding range. — The black-throated green warbler breeds north 

 to central western and northeastern Alberta (Grande Prairie, Peace 

 River and Chipewyan) ; central Saskatchewan (Big River and Emma 

 Lake) ; southern Manitoba (Brandon and Hillside Beach) ; southern 



