the whtte-winged black teen 71 



Order Lariformes. 

 Palate sehizognathous. Front toes fully connected by webs. 

 Bill simple. Primaries 10 large and visible, one minute, 

 concealed. Aftershaft to contour feathers. Oil-gland tufted. 

 Rectrices 12. Nestlings covered with down when hatched, soon 

 able to run. Eggs not more than three ; spotted or scrolled with 

 dark on a lighter ground. Coastal or marine aquatic birds. 



Family Laridce. 

 Bill without a cere. Sternum with two notches on each side 

 behind. Claws feeble or moderate. 



Sub-family Sternince. 

 Bill straight, rather slender; both mandibles of about equal 

 length. Tail, slightly or distinctly forked. 



Key to the Genera. 



A. Tail from nearly square to distinctly forked. 



a. Tail feathers rounded. Tail short. 



Bill small: webs indented. Hydrochelidon. 



6. Outer tail feathers longest, pointed. 



Tarsus very long, longer than mid-toe and claw. 



Bill robust. Gelochelidon. 



Tarsus short. 



Tail very short, less than one-third win^. 



Bill exceptionally stout and deep. Hydroprogne. 



Tail at least half wing, usually longer. 



Bill compressed and slender. Sterna. 



B. Tail graduated, feathers pointed, outer pair of rectrices 



shorter than next pair, 

 u.. Middle toe and claw longer than exposed culmen. 



Colour grey. Procelsterna. 



h. Middle toe and claw shorter than exposed culmen. 



Bill strong, decurved. Anous. 



Bill slender and long. Micranous. 



Bill stout at the base, pointed. Gygis. 



The White-winged Black Tern. 



Hydrochelidon leucoptera. 



Central Europe to Central Asia and China in summer, and in winter 

 to Australia, New Zealand, and Africa. 



Head, neek and upper parts glossy black; coverts on carpal joint 

 white, wing-coverts and primaries dark grey; tail white; underparts 

 black, under wing-coverts black. Total length 9.3 inches, culmen 1.1., 

 wing 8.2, tail 3.1, tarsus 0.7.5. When moulting the bird is parti-coloured. 



Nest made of reeds and water-plants on floating vegetation 

 in swamps. The clutch is three ; the eggs vary in colour, but are 



