696 A PRACTICAL HANDBOOK OF BRITISH BIRDS. 



brown -black, crown lightly marked with three narrow but irregular 

 streaks, a few spots or short streaks behind eye and on nape, rest 

 of upper -parts rather more strongly marked with two fairly well- 

 defined parallel streaks down mantle with short streaks or long spots 

 on each side and similar marks on back and rump and proximal 

 portion of wing, distal portion of wing uniform buff shading to 

 white at tip ; lores and under eye white tinged buff ; rest of under- 

 pays white but throat with varying amount of grey, sometimes 

 confined to tips of down, but sometimes whole throat dark smoke - 

 grey but never so dark as in Common and Arctic Terns and not 

 extending to chin or lores. Down is replaced by juvenile feathers to 

 tips of which it clings. 



Juvenile. — Fore -head and back of neck white, crown pale grey, 

 mantle darker grey, all feathers with tips washed sandy-buff, those 

 of crown and nape finely streaked brown-black, those of mantle 

 mostly with dark brown shaft -streaks and often subterminal brown 

 mottlings or patches, tips paler buff, scapulars with sometimes 

 more defined dark brown wedge-shaped subterminal patches ; back, 

 rump and upper tail-coverts ash-grey, feathers with faint buff tips 

 and indistinct dark subterminal marks ; greyish -black line round 

 and behind eye ; under-parts white ; tail-feathers grey with brown 

 wedge-shaped marks at tips and slight buff tinge ; wing-feathers 

 as adult but darker and duller, inner primaries with white edging 

 at tip, innermost secondaries and inner wing-coverts as scapulars, 

 rest of wing-coverts with only faint buff tips and brown shaft- 

 streaks and mottlings. 



First ivinter. — Like adult winter except for retained brown- 

 tipped juvenile tail-feathers, blacker and worn primaries and dark- 

 tipped primary-coverts. The juvenile body-feathers, lesser and 

 median wing-coverts, some innermost secondaries and greater 

 coverts, central and sometimes some other tail-feathers are moulted 

 Sept .-Dec. but not rest of tail or wings. Summer. — Moults appar- 

 ently later than adult and apparently not all wing- and tail-feathers 

 are moulted. From few examples examined becomes like adult 

 summer, but w T hen first grown black feathers of head are narrowly 

 edged white at tips, some old worn tail-feathers are left, primaries 

 and primary-coverts often as first winter. 



Measurements and structure. — £ wing 315-332 mm., tail : outer 

 feather 120-138, central 80-98, depth of fork 30-48, tarsus 33-37, 

 bill from feathers 34-41 (12 measured). 2 wing 300-330. Primaries : 

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

 longest, 3rd, 18-25 mm. shorter, 4th 42-50 shorter, 5th 62-75 

 shorter ; outer web of outer primary very narrow. Outer second- 

 aries shorter than inner primaries, inner ones about as long as 7th 

 primary, tips of outermost rather square, but of rest sharply sloped 

 off. Tail forked, 12 feathers, tips of outer tapering to rounded 

 point, rounder and shorter in juvenile. About quarter of tibia bare, 

 tarsus rather long, toes shorter, three front ones connected by 

 concave web, hind toe free, claws curved and somewhat dilated, 



