84 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I50 



and tropical areas, including islands in addition to widespread range 

 over the continents. 



The many subspecies that are recognized may be segregated in 3 

 major assemblages, one for Africa, Asia, Australia, and islands in 

 the Indian and Pacific Oceans ; one for North America, Central 

 America, and the West Indies; and one for South America. These 

 three, obviously closely related, form a superspecies that many tax- 

 onomists treat under one specific name, because of the general simi- 

 larity found throughout the many forms. 



While their close relationship is obvious, at the same time the popu- 

 lations of South America, and of the New World outside that con- 

 tinent, have certain characteristics that distinguish them from those 

 of the Old World. Clearer imderstanding of them is attained by 

 separating them as morphological entities under 2 specific names — 

 Butorides virescens and B. striatus — rather than uniting all under 

 one specific heading as Butorides striatus. 



The virescens group is characterized by chestnut to bright rufous 

 brown of the sides of the head and neck, and general darker color of 

 the back, particularly in the adult. Three subspecies in this assem- 

 blage are recognized in Panama. 



These small herons are widely distributed wherever there is water, 

 from sandy beaches where they take refuge in the bordering thickets 

 and mangrove swamps, back along the rivers to the smaller tributaries. 

 They watch for food along the water's edge, standing motionless or 

 walking slowly and stealthily. Often they remain quiet except for an 

 occasional downward jerk of the tail until closely approached, and then 

 fly with protesting squawks, the most vociferous of the tropical 

 herons. As small boats pass it is usual for them to climb back among 

 the low branches of trees overhanging the water until they are se- 

 curely hidden. 



Locally they are often called carga manteca; on the Rio Indio they 

 were known as coquito. 



BUTORIDES VIRESCENS VIRESCENS (Linnaeus) 



Ardea virescens Linnaeus, Syst. Nat., ed. 10, vol. 1, 1758, p. 144. (South 

 Carolina.) 



Characters. — Sides of neck dark chestnut-brown; larger; wing, 

 males 176-186 mm., females 172-186 mm. (maximum variation). 



Measurements (taken from a small series of migrant birds from 

 Mexico and Panama). — Males (5 specimens), wing 176-180 (179.1), 



