72 Zoology of Colorado 



is a larger bird, with a rounded tail. It was discovered by Say on 

 Plum Creek, near Castle Rock. The White-winged Dove (Mel- 

 opelia asiatica mearnsi) is recorded as an accidental visitor. In 

 spite of the specific name, it is a species of the warmer parts of 

 America. 



ACCIPITRES 



The Cathartidae are represented by the Turkey Vulture 

 (Cathartes aura septentrionalis of Wied), easily known by the red 

 naked head and neck. It is a common bird, but not obtrusive 

 as it is in some places where it is protected as a scavenger. A 

 single specimen of the Black Vulture (Coragyps urubu) was obtain- 

 ed in Boulder, and is in the University Museum. The Pandi- 

 onidae have a single representative in the American Osprey 

 (Pandion haliaetus carolinensis), which is not uncommon. It 

 has the outer toe reversible, and the claws all approximately the 

 same length, characters which separate it from all the Falconidae. 

 It feeds entirely on fish. The Falconidae* are well represented 

 with ten genera. Two of these are large, the wing over 1 7 inches, 

 and are eagles. Although the Golden Eagle (Aquila chrysaetos) 

 was described by Linnaeus from Sweden, and extends thence 

 right across Asia and America, it has not split up into subspecies 

 in this long range. The Bald Eagle or White-headed Eagle (Hal- 

 iaetus Ieucocephalus) extends across the United States, but there 

 is a distinct subspecies in the northwest. In Colorado, the Golden 

 Eagle is the commoner of the two. 



The genus Falco stands apart by the prominent tooth-like 

 projection on the cutting edge of the upper mandible, and is also 

 peculiar for the circular nostrils, with a central bony tubercle. 

 Our four species have been placed by recent authors in as many 

 genera. The larger birds, with only the outer primary feather 

 emarginate, are the Prairie Falcon (F. or Hierqfalco mexicanus) 

 and the Duck Hawk (F. or Rhynchodon peregrinus anatum). The 

 former is clay brown above, below with dusky linear spots; the 

 latter slaty-blue above when adult, but blackish, edged with tawny, 

 when young. The smaller forms (wing under 1 inches)** have 



*Sometimes divided into two families, Falconidae and Buteonidae. On this basis, Falco 

 in the broad sense, alone represents the Falconidae in our fauna. 



**The wing in birds is measured from the front of the bend cf the wrist joint to the tip of 

 the longest feather. 



