THE WHITE-WINGED BLACK TERN. 693 



slate-grey and innermost as lower -mantle, all becoming browner by 

 wear ; primary-coverts pearl-grey, becoming brown by wear ; 

 greater and median coverts pale slate-grey as lower-mantle ; lesser- 

 coverts dark slate-grey, edged whitish as upper-mantle. This 

 plumage is acquired by complete moult commencing sometimes 

 June, sometimes not until Aug., complete sometimes Aug. but often 

 not until Nov., Dec, or even Jan. Summer. Male. — Another 

 complete moult commences sometimes Dec. but usually later and 

 complete Ap -May or even June. Whole head, neck, and throat 

 all round and extending on to upper-mantle glossy blue-black ; 

 mantle, back, and scapulars blackish-slate sometimes black ; rump 

 and upper tail-coverts white ; under -parts black ; under tail- 

 coverts white ; axillaries black ; most under wing-coverts black 

 but lower series and those round edge of wing pale grey to whitish ; 

 tail white, when fresh often with ash-grey mottlings at tip ; 

 primaries as winter ; secondaries and greater coverts slate -grey, 

 darker on inner feathers ; median coverts paler ; lesser coverts 

 white. Female. — As male but head and neck not quite so 

 glossy, tail-feathers considerably mottled ash-grey and central 

 pair grey. 



Nestling. — Like that of C. niger (only one seen). 



Juvenile. — Like that of Black Tern but rump white or nearly 

 white, not slate-grey, and upper tail-coverts paler ash-grey ; no 

 dark brown patches on sides of breast but some feathers very rarely 

 tipped pale brown ; primaries with outer webs paler pearl -grey and 

 purer white on inner webs ; greater and median wing-coverts paler 

 ash-grey ; lesser coverts with broader hoary fringes. 



First winter. — Like adult winter except for brown tips of 

 unmoulted juvenile tail-feathers and innermost secondaries, 

 brown lesser coverts and worn and brown- 

 ish greater and median coverts, also fre- 

 quently a few juvenile body - feathers 

 unmoulted. The juvenile body-feathers 

 and central pair of tail-feathers are 

 moulted Aug -Dec. but not rest of tail 

 nor wing-feathers nor wing-co verts. First _.„ ... __.. . , _, . 



& . . ° 1 Bill of the White-winged Black 



summer. — A complete moult commences Tern (Chudonias leuoopterus.) 

 Jan. and bird usually becomes exactly like 



adult winter but occasionally considerable amount of plumage as 

 adult summer is acquired. 



Measurements and structure. — $ wing 200-218 mm., tail : outer 

 feather 67-75, central 58-67, depth of fork 5-11, tarsus 19-22, 

 bill from feathers 23-24 (12 measured). $ wing 192-210. Primaries : 

 1st pointed, narrow, and about two-thirds primary-coverts, 2nd 

 longest, 3rd 5-12 mm. shorter, 4th 18-26 shorter, 5th 34-42 

 shorter. Other structure as C. niger but tail less deeply forked 

 and tips of outer feathers rounder, bill shorter and rather less 

 slender, and webs between toes more deeply incised even than 

 in C. leucopareius. 



