24 Birds of Colorado 



Common Tern. Sterna hirundo. 



A.O.U. Checklist no 70— Colorado Record— Cooke 09, p. 314. 



Description. — Resembling the Arctic Tern in the arrangement of 

 the coloration of the tail-feathers, but with a longer tarsus averaging 

 longer than the middle toe without claw, and with the dark bands 

 on the inner web of the outer primary much more distinct and wide, 

 averaging -25 to '30 instead of -12 to -15 ; bill red, usually with dusky 

 tip, feet vermilion. Dimensions about the same. 



Distribution. — A common species found over the greater part of tho 

 world north and south ; breeding chiefly in arctic circumpolar regions. 



One example, taken May 14th, 1908, at New Windsor by Geo. 

 Osterhout, was sent to Cooke for identification. This is the only 

 Colorado record. 



Arctic Tern. Sterna paradiscm. 



A.O.U. Checklist no 71— Colorado Records— H. G. Smith 96, p. 48 ; 

 Cooke 97, p. 51. 



Description. — Closely resembling Forster's Tern but smaller, though 

 with a longer wing and with the outer web of the outer tail-feather 

 grey or dark and the inner web white, instead of the reverse ; under- 

 parts slightly paler than the mantle but hardly white ; bill red without 

 dusky tip, feet vermilion. Length 14 — 17, varying with length of 

 tail; wing 10-0; tail 2*5, to longest feather 6-5 to 8-5; culmen 1-20; 

 tarsus '65. 



Distribution. — Breeding in the circiunpolar regions of the Old and 

 New Worlds ; in America from Alaska and Labrador south to 

 Massachusetts. In winter ranging widely throughout the world's 

 coasts to South Africa and South America, as well as in many parts 

 of the United States. 



The Arctic Tern is a rare straggler in Colorado. An example killed 

 at Marston's Lake near Denver in the spring of 1887 was identified 

 as this species by Ridgway (H. G. Smith) ; while a second, an adult 

 male, was taken by W. G. Smith at Loveland, July 9th, 1889 (Cooke). 



Genus HYDROCHELIDON. 



Closely allied to Sterna but with a very short tail, less than half 

 the wing and very slightly forked ; with feeble legs, the webs much 

 indented so that the toes appear to be only half webbed ; lower-parts 

 of the body always black, or very dark grey in the breeding season. 



Four species, only one in North America. 



