55 

 Subfamily — Sterninae. Terns. 



General Description. The Terns, or Sea Swallows as they are sometimes called, are 

 smaller, lighter, and of more graceful build and habit than the Gulls. 



Distinctions. The bill, lighter, and more slender than that of the Gulls (See bill, 

 Figure 5, p. 18), and the forked tail are characteristic of the Terns and will usually 

 separate them without difficulty. All Canadian species have a more or less forked tail 

 and all but one (the Black Tern) in summer adult plumage have a sharply-defined black 

 cap. The forking of the tails of young birds, though beginning to show early in their 

 development, does not reach its maximum until after they leave for the winter; hence 

 through the summer and autumn many individuals will be seen with much smaller 

 forks than the measurements indicate. 



Field Marks. The greater lightness of action on the wing and constant and rapid 

 aerial evolution; the fact that Terns constantly dive from the wing, and the habit of 

 commonly turning the bill straight down towards the water intead of carrying it on a line 

 with the body are characteristic. The forked tails and black caps are also good recognition 

 marks for adults. 



Nesting. Whereas Gulls seem to prefer rocky shores upon which to breed, the Terns, 

 except Forster's and the Black, favour sandy beaches, laying their eggs in a smooth circle 

 of pebbles without other nest preparation. 



Distribution. As a subfamily, Terns are more southerly in distribution than Gulls, 

 though at least one species, the Arctic Tern ; has been found as far north as man has ever 

 gone. All our species migrate, none remaining in eastern Canada through the winter. 



One has only to watch a flock of Terns feeding to recognize the appro- 

 priateness of the popular term Sea Swallow. Their active grace and dainty, 

 pearl-like colours are a joy to the nature lover. Terns are on the whole 

 less marine in their habits than Gulls and are not as often seen far from land. 

 They haunt harbours, shores, and beaches, and live largely upon small 

 fish caught near the surface by quick, sudden dives from the wing, but 

 they are not scavengers. In these dives the birds plunge in head first with 

 a splash of white spray in which for a moment they disappear, but unlike 

 Gannets and Cormorants they never go far under water. 



Genus — Sterna. Terns. 



64. Caspian Tern. fr. — la sterne caspienne. lb grand esterlette. Sterna 

 caspia. L, 21. (Forking of tail 1-50.) 1 The largest of our Canadian Terns. In colour 

 very similar to the Common Tern (See p. 56). 



Distinctions. Large size of this Tern is characteristic. There are two other equally 

 large species, but they are too rare to require more than passing mention here. The Cas- 

 pian Tern is as large as some of the smaller Gulls; but its bill though comparatively heavy 

 for a Tern is too graceful and tapering to be gull-like. 



Field Marks. Characteristic Tern coloration, and habit and size make the best field 

 marks. A large Common Tern with less deeply forked tail. Its voice is utterly unlike 

 that of the smaller species being louder and much hoarser. 



Nesting. On sandy beaches, or rocky or gravelly islands. 



Distribution. A nearly cosmopolitan species. Found in the Old as well as the New 

 World. Occurs rather irregularly all over Canada, but its known nesting stations are 

 few and scattered over the continent from lake Winnipeg to Labrador. 



The peculiarly disconnected and irregular distribution of this beau- 

 tiful Tern suggests that it is a gradually disappearing species. This is 

 greatly to be deplored as it is one of the most beautiful of our sea-birds 

 and it is hoped that careful conservation of its few remaining breeding 

 stations will be inaugurated so that it will continue to adorn our waterways. 



> This measurement shows the difference in length between the middle and outer tail feathers. A great part of 

 the total length of these birds is in the greatly elongated outer tail feathers and these do not reach their maximum 

 in juvenile birds. Hence this figure is given to correct the oftentimes greatly misleading nature of the usual length 

 measurement. 



