ARCTIC TERN. 307 



exact locality of the colony is frequently changed from 

 season to season. From a very long and wide experience 

 of the habits of this Tern, I am of opinion that the bird 

 never makes a nest of any kind, beyond a mere hollow, 

 which is as often due to accident as to design. No 

 lining is ever used. The eggs also are more generally 

 laid nearer to the water than those of the Common 

 Tern. Any little depression in the coarse sand or 

 shingle, on the line of drift, among pebbles, or on the 

 bare ground or rock, serves as a receptacle for the eggs. 

 The actions of this Tern at the nest are precisely similar 

 to those of the preceding species. The eggs are seen 

 with difficulty, owing to their harmonizing with sur- 

 rounding tints. 



Range of egg colouration and measurement: 

 The eggs of the Arctic Tern are two or three in number, 

 and vary considerably in colour. They vary in ground 

 colour from buff or buffish-brown to olive, or even pale 

 bluish-green, blotched and spotted with dark brown 

 and ochraceous brown, and with underlying markings 

 of gray. The distribution of the markings runs through 

 much the same variation as those of the preceding 

 species, but blotches are more general. Average 

 measurement, 1*5 inch in length, by it inch in breadth. 

 Incubation, performed by both sexes, lasts from twenty- 

 one to twenty-three days. 



Diagnostic characters : The eggs of the Arctic 

 Tern are distinguished from those of the Common 

 Tern, the only species with which they are likely to be 

 confused, by their more elongated shape, smaller size, 

 bolder markings, and proneness to olive tints. Care, 

 however, should be exercised in identifying them 



