50 BRITAIN^S BIRDS AND THEIR NESTS. 



average. They are also more variable in colour ; but 

 two types predominate — a light type, greener than is 

 usual for the Common Tern's eggs ; and a brown type, 

 darker than the typical buffish-brown egg of the Common 

 species. The Arctic Tern's eggs are also more boldly 

 marked on an average, blotches being as typical as 

 small spots are of the other's. But, as we have said, 

 no single egg, however typical looking, can be ascribed 

 with more than probability to its particular species. For 

 certainty the adult bird must be identified. 



One point of special interest about the Arctic Tern is 

 that it has, as far as is known, the greatest latitudinal 

 range of any vertebrate animal. In the northern summer 

 it is found as high as 82° N. lat., and in its winter- 

 quarters it was found in the Antarctic summer in 74° 1' 

 S. lat. by the Scottish Expedition of 1902-4. 



THE ROSEATE TERN 



(Sterna dougalli). 



The Roseate Tern is very similar to the Common and 

 Arctic species, but has a longer, chiefly black, bill, a 

 paler mantle, and in the breeding season a rosy tint on 

 the breast feathers. It formerly nested on the coast and 

 islands on the west side of Britain, from the Scilly Isles 

 to the Cumbraes in the Firth of Clyde, at a few places 

 in Ireland, on the Fame Islands, and perhaps on the 

 coast of Moray. Some years ago it had practically 

 ceased to breed at any of these places owing to persecu- 

 tion, and perhaps to the increase of the stronger 

 Common species ; but efficient protection was afforded it 

 in time to allow it to re-establish itself in some places, 

 notably on the Fames and on the Welsh coast. Its 



