432 STERNID^ HYDROCHEL1DON 



Description. Adult in breeding plumage. Head all round, 

 back and rump, underparts as far as the vent, flanks, axillaries 

 and under wing-coverts black ; coverts along the carpal joint white, 

 becoming slaty on the other coverts and quills ; the four outer 

 primaries sooty-black on the outer webs, with a white streak down 

 the middle of the inner web, shafts white ; upper and under tail- 

 coverts, vent and tail white ; bill livid-red ; feet orange-red ; web 

 between the toes strongly indented. 



Length about 8-5 ; wing 7-75 ; tail 2*5 ; culmen -95; tarsus '75. 



The sexes are alike ; in non-breeding plumage the crown of the 

 head and nape are white mottled with black, while the underparts 

 and axillaries are pure white ; bill black. Young birds are some- 

 what similar to the adults in non-breeding plumage, but the upper 

 tail-coverts are always white, though the tail itself is grey. 



Distribution The White-winged Black Tern is found, through- 

 out the northern summer, in Central and Southern Europe and 

 Central Asia as far as China; during the northern winter it migrates 

 southwards to Australia, New Zealand and Africa. 



In Africa it has chiefly been met with in the east and south, 

 having been recorded from most of the larger lakes such as Albert 

 Edward and Tanganyika. Beyond an example in the British 

 Museum stated to have been obtained by Mr. Layard, I know 

 of no other notice of its occurrence in the Colony proper, but it 

 appears to become more abundant further north. 



The following are the recorded localities : Orange Eiver Colony 

 Kroonstad, December (Symonds) ; Transvaal Potchefstroom, 

 June, July and November (Ayres) ; Bechuanaland (S. A. Mus.) ; 

 German South-west Africa Omanbonde (Andersson in Bt. Mus.) ; 

 Portuguese East Africa Chicowa September and Zumbo, Novem- 

 ber on the Zambesi (Alexander). 



Habits. This Tern is generally seen in considerable flocks 

 hawking for insects, on which it chiefly subsists, over marshes and 

 lagoons and even on temporary rain pools ; its flight is somewhat 

 slow, uncertain and heavy. Andersson states that it feeds on frogs' 

 spawn and snails as well as insects. Alexander saw large flocks 

 passing down the Zambesi presumably on migration during the 

 months of November, December and January. They were in 

 winter dress. It is not probable that this bird will be found breed- 

 ing in South Africa. 



