WHITE TERN. 105 



Leucanous albus. WHITE TERN. 



[Sterna alba Span-man, Mus. Carlson, fasc. r., No. 11, 1786 : " India oriental!, at Promon- 

 torium Bonae Spei, etc. " = Ascension Island. Extra-limital.] 



Gould, Vol. VII., p. 30 (pt. xxxv.), Dec. 1st, 1848. Mathews, Vol. II., pt. 4, pi. 119, Nov. 1st, 

 1912. 



Gygis alba royana Mathews, Birds Austr., Vol. II., p. 433, Nov. 1st, 1912 : Kermadec Islands 

 DISTRIBUTION. Probably as straggler to east coast of Australia. 



Adult male. Entire upper- and under-surface of body ivory-white ; short 

 feathers surrounding the eye black ; shaft-lines of primary -quills dark brown, 

 somewhat darker and inclining to black on the shafts of the tail-feathers ; bill 

 black at tip, base blue ; iris brown ; tarsi, toes and webs yellow. Total length 

 330 mm. ; culmen 45, wing 250, tail 110, tarsus 16. 



Adult female. Similar to the adult male but somewhat smaller. Total length 

 260 mm. ; culmen 40, wing 243, tail 108, tarsus 14. 



Immature (half grown). Retaining down adhering to back of head, sides of rump, 

 throat, etc. ; nape with pale rusty-brown tipping to white feathers, back similarly 

 barred with rusty tips, scapulars and inner secondaries prominently so marked 

 with darker bars, wing-coverts with rusty edges ; black spots in front of eye ; rest 

 of plumage snow-white. Iris dark brown, feet dark blue with cream webs, bill 

 greyish-blue and black. (Norfolk Island.) 



Nestling (a few days old}. Shows down to have been mottled and not uniform as 

 commonly accepted ; a large black patch above and extending behind the eye, pale 

 brown line above, and then black markings towards nape, greyish-brown on fore-head 

 with lighter edge ; back dark brownish-grey with indistinct pale blotches ; wings 

 similarly blotched, method of disposal of blotches indistinguishable ; throat dark 

 grey, abdomen lighter grey. Iris, very dark brownish-grey, feet light blue, webs 

 flesh, bill bluish-black all over. (Idem.} 



Nestling. Covered with black down. From dark brownish-grey to very light 

 grey, or almost white. 



Nest. The egg is laid in a depression on the branch of a tree or on a point of rock. 



Egg. Clutch, one ; ground-colour stone, blotched all over with reddish-brown 

 and lavender. Some examples have a resemblance to the eggs of Chlamydera ; 

 -axis 42-44 mm., diameter 33. 



Breeding-season. October to February. 



Distribution and forms. Throughout tropical seas breeding on isolated islands. 

 Mathews in 1912 suggested half a dozen subspecies and since then no critical work 

 appears to have been done on this species. Mathews proved that Sterna alba 

 Sparrman must be used for this species and fixed the type locality as Ascension 

 Island. The North Pacific form differs in dark coloration of the shafts of the 

 primaries, and different shape and parti -coloured bill, the Atlantic form having 

 a wholly black bill, slenderer and narrower at base. For this North Pacific form 

 Leucanous albus candidus (Gmelin) may be used, the type locality being Christmas 

 Island, to which may be referred the Hawaiian Group birds ; series are not available 

 to determine whether the Caroline and Marianne birds are separable, but, if so, 

 their name would be Leucanous albus kittlitzi (Hartert) ; Kermadec breeding birds 

 have longer wings and longer bills and bear the name Leucanous albus royanus 

 (Mathews) ; to this race has been assigned Norfolk Island birds and these would 

 occur on the east Australian Coast ; Leucanous albus pacificus (Lesson) can be used 

 for the birds from the Society Group and Samoa, which have shorter wings but 

 longer bills than the preceding. Probably other races occur in the Pacific Ocean. 

 The Indian Ocean form, breeding at the Seychelles, can be called Leucanous albus 

 monte Mathews, differing in their shorter wings from the Pacific forms but having 

 bills as long as L. a. royanus. All Atlantic birds are classed as Leucanous albus albus 



