A REVISION OF THE SUBSPECIES OF THE GREEN HERON 

 (BUTORIDES VIRESCENS [LINN^US]). 



By Harry C. Oberholser, 



Assistant Ornithologist, Biological Survey, Department of Agriculture. 



I The following revision of the forms of Butorides virescens (Lia- 

 naeiis) was undertaken at the instance of Mr. H. W. Henshaw, Chief 

 of the Biological Survey. Its purpose is to clear away, as far as the 

 present material will permit, the confusion now existing with regard 

 to the relationships and distribution of the various races, and thus 

 to assist in preparing the way for a bulletin on the migration and 

 distribution of North American herons, now in course of preparation 

 by Prof. W. W. Cooke, and soon to appear as a publication of the 

 Biological Survey. 



For this task the A\Titer has been able to examine 568 specimens, 

 including the types of all the forms of this species, excepting Buto- 

 rides virescens virescens, Butorides virescens frazari, and Butorides 

 virescens maculatus; and comprising the entire series of green herons 

 in the collections of the United States National Museum, including 

 that of the Biological Survey; the American Museum of Natural 

 History; the Academy of Natural Sciences of Philadelphia, includ- 

 mg that of Mr. H. W. Fowler; the Museum of Comparative Zoology 

 in Cambridge, Massachusetts, including the Bangs collection; and 

 the collection of Dr. Jonathan Dwight, jr. ; together with a few im- 

 portant birds from the Carnegie Museum of Pittsburgh, Pennsylva- 

 nia, and the Field Museum of Chicago. To the authorities of these 

 institutions, particularly the United States National Museum, and 

 to the individuals mentioned, as well as to the custodians of the 

 various bird collections, especially Dr. Charles W. Richmond, of the 

 United States National Museum, the writer takes this occasion to 

 offer expression of his sincere appreciation of facilities afforded. 



The various races of Butorides virescens with their intricate rela- 

 tionships and rather peculiar geographical distribution, have always 

 presented a difficult problem. Previous authors who have wrestled 

 with these difficulties have lacked sufficient material, particularly 



Proceedings U. S. National Museum, Vol. 42— No. 1916. 

 20441°— Proc.N.M.vol.42— 12 34 529 



