62 



BULLETIN 86, UNITED STATES NATIONAL MUSEUM. 



that is, typical. Specimens from Germania, GreybuU, and other 

 localities in northern Wyoming are darker above, thus verging some- 

 what toward Chordeiles virginianus hesperis, though still much too 

 pale and brownish above for that form. Examples from southeast- 

 ern Wyoming show some tendency toward intergradation with CTtor- 

 deiles virginianus sennetti. The few individuals from Henrietta in 

 central northern Texas examined are in color typical CTiordeiles 

 virginianus howelU, but in size appear to be smaller, in this showing 

 a close approach to Chordeiles vi/rgimdanus aserriensis '■ of southern 

 Texas; but the small series and the worn and otherwise poor con- 

 dition of the specimens may be responsible for at least part of the 

 difference. Birds which apparently represent the breeding form of 

 Lee County, Texas, considerably farther south and near the known 

 breeding range of Chordeiles virginianus aserriensis,^ are, however, 

 larger, while those from northwestern Texas are of full size. The 

 differences in size that obtain in birds from the various parts of the 

 breeding range of the present race are observable in the following 

 average measurements : 



One adult male from Warsaw, Illinois (No. 98226, U.S.N.M.), 

 taken. May 20, 1884, and another from Grant County, Minnesota (No. 

 81564, Amer. Mus. Nat. Hist.), collected in the spring of 1877, seem 

 to be both practically typical Chordeiles virginianus howelli, though 

 apparently far out of the normal migration route of this form, and 

 thus of merely casual occurrence here. The present race undoubtedly 

 migrates regularly through Mexico and Central America to South 

 America, but there is only one certain record of its occurrence south 

 of the United States : a single individual from the Escondido Eiver, 

 in Nicaragua, 60 miles above BlueSelds, taken, September 17, 1892, 

 by Dr. Charles W. Richmond. 



The specimen (No. 6696, U.S.N.M.) that Prof. Spencer F. Baird 

 regarded as the type of Chordeiles virginianus henryi Cassin is still 



1 See p. 71. 



