LARIDAI—TERNS. 277 
Order GAVIA. 
Family LARIDA. 
Subfamily STERNINA. 
Genus HYDROCHELIDON. 
BLACK TERN. 
Hydrochelidon nigra (Zznz.). 
Adult (Summer) : Head and neck dark lead-grey, blackish 
on crown and nape; back, wings and tatl nearly uniform slate- 
grey, becoming whitish on the shoulders ; breast and abdomen, 
like head and neck, dark lead-grey ; under wing-coverts pale 
grey ; vent and under tail-coverts white ; tail distinctly, though 
not deeply, forked ; outer feathers on either side the longest ; 
bill black; legs and feet dark reddish-brown; irides dark 
brown. Length ro inches ; culmen 1°25 ; wing 8°5; tail 3°25; 
tarsus 0°65. 
Adult (Winter): Forehead, chin, throat and loral region 
white, otherwise as in summer, except for a few white bars 
across the breast. . 
Immature Birds: “Forehead, cheeks, and under surface 
of the body white; back, wings, and tail leaden-grey inter- 
mingled with brown” (Shelley). 
Distribution: Breeds in suitable localities throughout 
most of Europe south of the Baltic, also in North America. 
Winters in Africa and in South America as far as Chili. 
Habitat: Inland marshes and margins of lakes and rivers ; 
the sea-coast during migration. 
