378 BIRDS OF THE BRITISH ISLES. 



Caspian Gem. 



THE Caspian Tern (Sterna Caspia, Pallas) is a rare ab- 

 normal spring and autumn migrant to the British Isles, and 

 is found inhabiting the temperate and tropical zones. The 

 adult in summer has the crown and nape of the neck rich 

 black ; upper parts and tail, which is slightly forked, pearl- 

 grey; primaries, brownish, washed with grey; sides of the 

 head, front of neck, and rest of under parts, white ; irides, 

 dark hazel; bill, vermilion; legs and feet, black. Length, 

 from nineteen to twenty-one inches. The forehead and 

 crown of the adult in winter is white, streaked with black ; 

 behind the ear-coverts there is a dark patch. The young 

 in first plumage have ashy-brown mottlings on the upper 

 parts ; forehead and crown, white ; under parts, white. 



