540 BULLETIN 203, UNITED STATES NATIONAL MUSEUM 



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

 passim (Griscom), September 23; Sierra de Tecpan, September 26, 

 1933; Huehuetenango, September 19, 1934; Colomba, September 24, 

 1934. Costa Rica — San Jose (Underwood), September 25, 1898. 



"Late dates of spring departure from Central America are : Guate- 

 mala — passim (Griscom), April 26; Sierra de Tecpan, May 10, 1933." 



In El Sabador, Dickey and van Rossem (1938) record MacGilli- 

 vray's warbler as a — 



common midwinter visitant and spring migrant to the upper footliills and moun- 

 tains, from 2,300 feet on the Arid Lower Tropical Zone to 8,000 feet in the 

 Humid Upper Tropical. * * * MacGillivray's warblers did not arrive until 

 much later than 0. Philadelphia, but after the first week of December they 

 were to be found everywhere in underbrush in the higher foothills and moun- 

 tains. On Mt. Cacaguatique they were noted in ravine growth along water- 

 courses ; on Volcan de Conchagua among the pines in company with black- 

 throated green warblers ; on Volcan de San Miguel in the head-high grass of 

 the lava gullies ; and on Los Esesmiles in clearings and in natural open spaces 

 in the cloud forest. A fairly cool temperature rather than any particular plant 

 association seems to be the primary factor governing their choice of winter 

 quarters. 



DISTRIBUTION 



Range. — Southern Alaska, western Canada, and the United States 

 south to northwestern South America. 



Breeding range. — MacGillivray's warbler breeds north to southern 

 Alaska (Port Snettisham) ; central Alberta (probably Peace River 

 Landing, Lesser Slave Lake, and Edmonton) ; and southwestern Sas- 

 katchewan (Cypress Hills). East to southwestern Saskatchewan 

 (Cypress Hills) ; southwestern South Dakota (Black Hills) ; and 

 through the mountains of central Colorado to New Mexico (Alto and 

 Arroyo Hondo Canyon). South to southeastern New Mexico (Alto) ; 

 central Arizona (San Francisco Mountains and "Wliite Mountains) ; 

 northern and central Nevada (Galena Creek, Toyabe Mountains, and 

 Baker Creek) ; and central California (Paicines, Placerville, Yosem- 

 ite, Sequoia National Park, Kern River, 'Wliite Mountains, and 

 Berkeley). West to central California (Berkeley) ; northeastern Ore- 

 gon (Powder River Mountains) ; northwestern and central British 

 Columbia (Telegraph Creek, Doch-da-on Creek, Hazelton, Summit 

 Lake, and Yellowstone Lake) ; and southern Alaska (Boca de Quadra, 

 Bradfield Canal, and Port Snettisham). 



Winter range. — The species winters north to southern Baja Cali- 

 fornia (La Paz, El Triunfc, and Cabo San Lucas) ; southern Sonora 

 (rarely Alamos) ; and Nuevo Leon (rarely Monterrey). East to 

 Nuevo Leon (Monterrey) ; Guatemala (Lake Atitlan, Coban, Patulul, 

 and Duenas) ; Costa Rica (San Jose, Barranca, Buenos Aires) ; Pan- 

 ama (Volcan de Chiriqui and Colon) ; and northern Colombia (Antio. 

 quia, Santa Elena, and Bogota). South to Colombia (Bogota) ; El 



