74 Zoology of Colorado 



overhead. The tarsus is feathered to the toes in the American 

 Rough-legged Hawk (B. or Archibuteo lagopus sancti-johannis) 

 and in the Ferruginous Rough-leg (B. or A. ferrugineus). Both 

 are very useful, feeding on small rodents. In the normal phase 

 the belly has a black patch in the former, lacking in the latter, 

 which has thighs rufous with black cross-bands. Both are some- 

 times melanistic, the plumage black or sooty-black, but then the 

 American Rough-leg has a white forehead. The tarsus is half 

 feathered, with scutes in front only, in the Red-tailed Hawk (B. 

 borealis calurus) and Swainsons Hawk (B. swainsoni). In the 

 former the four outer primaries are emarginate on the inner web, 

 the latter only three. It is necessary to pay attention to these 

 characters, for the plumage of the birds varies greatly in color. 

 The Red-tail has the tail rich rufous, with a subterminal black 

 band; but in the young the tail has ten or twelve dusky black 

 bars and a white tip. A pale race (B. b. krideri) occurs in Eastern 

 Colorado, and a single specimen supposed to be from El Paso 

 County was referred to the race harlani of Audubon.* 



STRIGES 



The owls, flying by night, excepting Speotyto, are not likely 

 to be confused with any other birds. The Tytonidae, with the 

 claw of the middle toe serrate on inner edge, are represented only 

 by the American Barn-owl, Tyto alba pratincola, a rare bird with 

 us. The generic name Aluco, based on the same species, was 

 earlier used for a mollusc, so Tyto (1890) is available. The rest 

 of the owls fall in Strigidae, with no serration on claw of middle 

 toe, which is always longer than the inner one. The ear-tufts 

 are present in three genera, Bubo, Asio and Otus, but absent in 

 the others. The first of these genera consists of large owls, the 

 wing over 14 inches; in the second the wing is 10 to 12 inches, and 

 the toes are feathered to the claws; in Otus the wing is under eight 

 inches, and the toes are bristly or naked. These eared owls con- 

 stitute a prominent and important part of our avifauna, and some 

 of them show variations in plumage which have proved perplexing. 

 The Western Horned Owl {Bubo virginianus occidentalis of Stone) 



*Mr. Warren writes that Aiken bought the skin from Borcherdt in Denver, when he first 

 came to Colorado, and the locality is wholly uncertain. The specimen appears to have been 

 lost. This record is therefore of no value, but Lincoln in 1920 recorded harlani from Littleton. 



