4 
ALLEN’S naturalist’s LIERARY. 
mantle ; the head and nape blackish, the forehead whiter ; 
round the hind neck a broad collar of white ; sides of face and 
under surface of body pure white, excepting for a patch of 
ashy-brown on each side of the upper breast. 
Adult Male. — General colour above slate-grey, a little paler on 
the wing-coverts, the small coverts round the carpal bend of 
the wing being white ; the bastard-wing, primary-coverts, and 
quills dark slaty-brown, externally frosted with light ashy-grey, 
and paler grey on the inner web, the shafts of the primaries 
white ; the upper tail-coverts and tail-feathers slightly paler 
slate-colour and inclining to pearly-grey ; crown of head black, 
overspreading the hind neck towards the mantle; the under 
surface of the body leaden-black, deepening on the throat and 
chest ; thighs, sides of lower flanks, under tail-coverts, as well 
as the under wing-coverts, white ; the lower greater coverts pale 
pearly-grey like the quill lining ; axillaries leaden-grey ; bill 
black ; feet reddish-brown. Total length, 9-5 inches ; culmen, 
1-25 ; wing, 8'4; tail, 3'i5 ; tarsus, o-6; middle toe and claw, 
o'8s. 
Adult Female. — Similar to the male, but slightly paler in 
colour. Total length, 9-6 inches; wing, 8 t. 
Adult in Winter Plumage. — Distinguished by the white under 
surface from the summer plumage, the forehead being white, 
and the hinder crown and centre of the nape black, the feathers 
having hoary-white margins ; sides of face, sides of neck, and 
a collar round the hind neck white, like the under surface of 
the body. 
Characters. — The adult Black Tern is easily recognised from 
the other British species of Hydrochelidon, in summer plumage, 
by its pale grey under wing-covert.s, these being black in 
H. leucoptera and white in Jl. hybrida. The grey upper 
tail-coverts and tail distinguish it from H. leucoptera, which is 
black underneath, not dark leaden-grey as H. nigra is. From 
H. hybrida it may be distinguished by its black bill and black 
sides of the face. 
In winter plumage the three species are more difficult to 
discriminate, but H. nigra and H. hybrida have the tail grey 
and the rump also grey like the back, H. nigra is a smaller 
