Order LARIF0BME8 
No. 131. 
Family LARIDM. 
THALASSEUS BEKGII GWENDOLENiE. 
WESTEALIAN CRESTED TERN. 
Sterna bergii Gwendolen.®* Mathews, Nov. Zool., Vol. XVIII., p. 208, 1912 ; South- 
west Austraha. 
Sterna bergii Grant, Ibis 1910, p. 185. 
Distribution. South-west Austraha. 
Adult male. Paler and larger than the preceding ; “ bill pale ochre yellow ; legs dark slate ; 
soles of feet yellowish; iris dark brown (almost black).” Guhnen (exp.) 72 mm., 
wing 380, tail 210, tarsus 30.5. 
Adult female. Similar to the adult male. 
Immature [before moulting into full breeding-plumage). Head more or less dark brown, 
feathers with white bases and whitish tips ; forehead and lores whitish with a few 
brown speckles ; a spot just in front of the eye dark ; a few brown tips to the 
feathers on the sides of the neck ; feathers of the bend of the wing whitish, 
greater wing-coverts dark brownish-grey ; median wing-coverts ashy-grey ; lesser 
wing-coverts darker ashy-grey. 
Immature [in change from juvenile plumage). A few brown-tipped feathers remain on the 
upper-back ; the majority of the feathers slaty ; the scapulars and median coverts 
however, show the juvenile-plumage to still predominate. 
Juvenile [young bird just ready to fly). The feathers of the head have white bases and tips, 
the middle being dark brown, the head having thus an even mottled appearance ; 
the sides and back of the neck are white, some of the feathers having brown spots 
on the tips, giving a speckled appearance. These brown tips become larger and 
more frequent on the feathers of the upper-back, with fewer but more strongly 
marked on the lower-back, rump, and upper tail-coverts ; the tail-feathers have 
white bases and white tips, the anterior portion brown in varying proportions ; 
the middle feathers are mostly grey, with a brownish marking towards their apices, 
but all the tips white ; the next pair have more brown, less grey, and less white 
tipping, and so on outwards ; the scapulars are marked hke the middle tail-feathers ; 
the bend of the wing is white ; the greater wing-coverts are deep brown with white 
tips ; the median white with brownish tips, the extreme tips, however, white again ; 
the lesser wing-coverts ashy-brown tipped with white ; the secondaries ashy-grey 
with white tips ; the primaries deep brown on the outer and half of the inner web ; 
the inner half white, distinctly marked off ; the remainder of the under surface 
white. 
Nest. A depression in the sand. 
Egg. Ground-colour stone, heavily blotched with dark reddish-brown ; axis, 60-61 mm., 
diameter 40-41. 
* Named after Miss Gwendolens Carter, as a mark of appreciation of the help given me by her father. 
350 
