57 



71. Arctic Tern. FR. LA STERNE ARC-PIQUE. Sterna paradiscea. L, 15-50. 

 (Forking of tail 4 50.) 1 Closely resembling the Common Tern (See above) in size and colour. 



Distinctions. The Arctic Tern has a little stronger greyish suffusion over breast and 

 underparts than the Common Tern. Bill is red to tip and feet and legs are very small and 

 weak. Its range separates it from Forster's Tern and there are only the Common and the 

 Roseate with which it can be confused, but the Roseate is too rare on Canadian waters to be 

 considered. 



Field Marks. There is no field mark that can be described by which this species 

 can be recognized with certainty, but the even red coloration of the bill is a fairly 

 reliable guide. In eastern Canada it is a sea-coast species, and it should be recorded on 

 eyesight evidence only where it is known to occur commonly. 



Nesting. Depression in sandy beaches. 



Distribution. Nearly cosmopolitan, but of eastern and Arctic distribution in Canada 

 and rarely if ever seen in the Great Lakes region. It is notable from haying perhaps the 

 greatest migration range of any species of bird. Though in summer it flies nearly to the 

 north pole, it winters as far south as the Antarctic continent. 



The remarks made under the heading of the Common Tern apply 

 here also, bearing in mind that this species is regularly only of extreme 

 eastern and Arctic distribution. 



Economic Status. The small size of the fry it takes and the known 

 abundance of such fish in the sea, render this species as harmless as any 

 of the other Terns. 



Genus Hydrochelidon. Black Terns. 



77. Black Tern. FR. LA STERNE NOIRE. Hydrochelidon nigra. L, 10. (Forking 

 of tail, 0-8.) 1 The smallest of our Common Terns, dark slate-grey deepening to dull 

 black on head, neck, and underparts. 



Distinctions. The above diagnosis is sufficient to separate summer adults. Winter 

 and immature birds have a dirty white face, throat, neck ring, and underparts and the 

 grey above is suffused with more or less brown. It is, however, always considerably 

 darker than corresponding plumages of other species. This fact and the small size of the 

 bird should be sufficient to differentiate it at all times. 



Field Marks. Size and coloration make this species easy to recognize in life. 



Nesting. On slight elevations such as old muskrat houses or floating debris in wet 

 marshes, nest of vegetable matter. 



Distribution. The American Black Tern is a bird of the interior, breeding from the 

 Great Lakes region westward. 



SUBSPECIES. The Black Tern occurs in both Europe and America in allied sub- 

 specific forms of which the European is the type. The American Black Tern C.n. sur- 

 inamensis is the only subspecies with which we are concerned. 



This is a bird of the inland marshes. It is rarely seen on the larger 

 bodies of water, but within its regular range no extensive expanse of 

 watery marsh is without it. Its general habits are much like those of the 

 other Terns. 



Economic Status. The insect content of this bird's food is probably 

 larger than that of the other Terns. In the south it is known to consume 

 the larvae of the cotton-boll weevil and it follows the ploughman of the 

 west for the grubs turned up. Therefore, we can venture to state that 

 it is probably actively beneficial. At any rate the fish it takes are mud- 

 inhabiting forms of small economic importance. 



1 See footnote, p. 56. 



