716 A PRACTICAL HANDBOOK OF BRITISH BIRDS. 



Nestling (Plate 10). — Down rather shorter than in Common 

 Tern with shorter fine hair-like tips. Upper-parts pale sandy-buff 

 mottled brown with no definite pattern but sometimes taking form 

 on crown of three narrow parallel streaks and on mantle of two ; 

 under -parts white, throat sometimes tinged pale sandy-buff. 



Juvenile. — Fore -head and lores sandy-buff ; dusky black line 

 round eye and short white patch over eye ; top of crown sandy-buff 

 spotted or streaked dusky-black, feathers being blackish sub- 

 terminally, nape and sides of crown behind eyes brown-black, 

 feathers very narrowly fringed buffish- white ; back of neck bufnsh- 

 white ; mantle and scapulars sandy-buff, feathers with U-shaped 

 brown subterminal bars, basal part of feathers grey and upper 

 scapulars more broadly barred, but lower scapulars ash-grey, 

 tipped white without bars ; back, rump, and upper tail-coverts 

 ash-grey (back darker), feathers tipped white (at first with buff 

 tinge) and sometimes with faint brown subterminal marks ; under- 

 pays white ; outer tail-feathers white, rest ash-grey, edged white 

 (tinged sandy-buff at first), and with dark brown subterminal 

 patches ; primaries as adult but much darker grey and white 

 edging at tips broader ; secondaries as adult but with darker shaft - 

 streaks ; primary-coverts, bastard-wing and feathers along front 

 edge of wing blackish -grey, fringed hoary ; greater coverts grey 

 fringed sandy-buff to white, innermost and innermost secondaries 

 barred as upper scapulars ; median coverts grey, tipped sandy-buff 

 and with faint brown subterminal marks ; lesser coverts dark grey, 

 fringed hoary. N.B. — Sandy-buff of upper -parts and wing-coverts 

 becomes almost white by wear. 



First winter. — Like adult winter but usually a few juvenile 

 body-feathers retained, tail-feathers, primaries, and secondaries as 

 juvenile but some innermost secondaries like adult, wing-coverts 

 mostly like adult but lesser coverts and feathers along front edge of 

 wing darker. The juvenile body-plumage, lesser and median wing- 

 coverts, innermost greater, and some innermost secondaries and 

 central tail-feathers are moulted Aug. -Oct. N.B. — Very few winter 

 examples examined. Summer. — A complete moult takes place as 

 in adult after which bird apparently becomes like adult but those 

 birds with 3 outer primaries blackish, lesser coverts rather dull 

 blue -grey and some dark feathers along edge of wing may be 1st 

 summer. 



Measurements and structure. — $ wing 164-180 mm., tail : outer 

 feather 75 (one 66)-95, central 43-48, depth of fork 23-50, tarsus 

 15-18, bill from feathers 27-32 (12 measured). $ wing 164-180, tail : 

 outer 74-85, central 42-48, fork 28-41. Juvenile $ and ? wing 

 160-173, tail : outer 56-65, central 42-46, fork 11-20. Primaries : 

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

 2nd longest, 3rd 5-14 mm. shorter, 4th 17-27 shorter, 5th 32-42 

 shorter. Rest of structure as Sandwich Tern but gonys very long 

 (about half length of bill) and very gently sloped up to tip, angle not 

 prominent. 



