NO. 1916. REVISION OF BUT0RIDE8VIRESCEN8—0BERH0L8ER. 531 



States, Mexico, Central America, and the West Indies to northern South 

 America. In the northern part of the Neotropical Region it inhabits 

 the Lower Tropical and Upper Tropical zones; in the southern portion 

 of theNearctic Region, the Lower Austral, Upper Austral, and Transi- 

 tion zones. The total number of its recognizable races becomes now 

 18, of which 12 are insular, most of them West Indian. The favorite 

 haunts of the species are the swamps, marshes, large and small streams, 

 both along the seacoast and in the interior; but not infrequently the 

 bird chooses dry upland for its nesting sites, though usually not far 

 from water, from which it obtains the greater part of its food. It is a 

 frequenter of the reedy or bushy marshes, sparsely wooded swamps, 

 the margins of bayou, lake, and stream, of damp thickets, and the 

 more or less open countiy, rather than of the deep forest. With the 

 exception of the northernmost three, Butorides virescens virescens, 

 Butorides virescens anthonyi, and Butorides virescens eremonomus ^, 

 all the forms appear to be permanently resident; but these three 

 perform extensive migrations. 



Some curiously close resemblances between widely separated races 

 may be mentioned, as of interest from an evolutionary point of view. 

 The bird from Swan Island, in the Caribbean Sea — Butorides virescens 

 saturatus — is colored much more nearly like Butorides virescens 

 frazari, from Lower California, than like Butorides virescens virescens 

 of the adjacent mainland. Also, Butorides virescens mesatus,^ from 

 Nicaragua, is, m size and color, more like the race from northern 

 Mexico, Butorides virescens eremonomus,^ than like the intervenmg 

 Butorides virescens virescens or the Costa Rican Butorides virescens 

 Jiypernotius.^ The bird inhabiting the Pearl Islands, in the Bay of 

 Panama, is, likewise, in appearance nearer Butorides virescens satu- 

 ratus, from Swan Island, than to Butorides virescens hypernotius ^ on 

 the neighboring mainland. The Bahaman Butorides virescens haha- 

 mensis is very different from both Butorides virescens virescens, from 

 Florida, and Butorides virescens cuhanus,'^ from Cuba, and, in color, 

 much more like Butorides virescens anthonyi of Arizona. The subspe- 

 cies living on the island of St. Christopher, Butorides virescens christo- 

 pTiorensis,^ is much more like Butorides virescens haliamensis than it 

 is like Butorides virescens cuhanus,^ which almost surrounds it ; and 

 Butorides virescens harhadensis,^ from Barbados, is much closer in color 

 to the geographically far distant Butorides virescens haliamensis than 

 to any of the several intervening races. Agam, the birds from the 

 islands of Martinique {Butorides virescens maculatus), St. Lucia 

 {Butorides virescens lucianus),'' and Grenada {Butorides virescens 

 grenadensisY are nearer in appearance to Butorides virescens cuhanus * 



