THE AUK: 



A QUARTERLY JOURNAL OF 



ORNITHOLOGY. 



Vol. xxii. January, 1905. No. 1. 



ROUTES OF BIRD MIGRATION. 



BY WELLS W. COOKE. 



I. Migration Route from Mexico to Texas by Water. 



Throughout the broad expanse of level land between the Alle- 

 gheny and the Rocky Mountains, bird migration is so uniform 

 that a species is expected always to appear first at the more south- 

 ern localities. An apparent exception to this rule is noted in the 

 case of several species whose recorded dates of spring arrival in 

 northern Texas are earlier than the corresponding dates many 

 miles to the southward. 



Thus the first Black and White Warblers {Mniotilta varia) 

 were seen near Corpus Christi March 21 (average of five years), 

 near San Antonio. March 15 (average of seven years), and in 

 northeastern Texas March 13 (average of four years) . The dis- 

 tance from Corpus Christi to latitude $t° in northern Texas is 350 

 miles, a distance that ordinarily is passed over by the Black and 

 White Warbler in about 17 days, since its average rate of travel 

 in the Mississippi Valley is not far from 20 miles per day. This 

 species therefore arrives in northern Texas some three weeks 

 earlier than would be expected from the records of its spring 

 appearance in southern Texas. The records for ten years give 

 March 21 as the average date of arrival of the Parula Warbler 

 {Compsothlypis america?ia) at San Antonio, while the corresponding 

 date 300 miles farther north is March 14. 



