GREY-HEADED MOLLYMAWK. 51 



wing-coverts white, more or less shaded with grey, the smaller coverts round the 

 margin black, like the upper wing-coverts ; quills below brown with white shafts, 

 which are blackish towards the tips ; bill uniform, gamboge -yellow, shaded with 

 orange on the hook and with a very fine line of black round the base of the mandibles ; 

 iris light brown ; feet delicate blue-grey, darker on the joints and interdigital 

 Webs ; claws white-horn colour. Culmen (exp.) 115 mm., depth at base 45, wing 

 510, tail 200, tarsus 78.5, middle toe 115. 



Adult female. Similar to the adult male. 



Young. Differs from the adult in having the head and neck ash-grey, and 

 the upper -surface of wings and interscapular region brownish-black, the smaller 

 wing-coverts with paler margins, the bill blue-black, and the legs and feet 

 bluish -grey. 



Nestling. Covered with long, thick woolly down, of a pale grey colour ; bill 

 brownish -black with yellowish-horn coloured tip ; legs and feet yellowish -white. 



Nest. A conical mound from 8 in. to 18 in. in height constructed of mud mixed 

 with vegetable substances, the cup-shaped depression is lined with finer materials. 



Eggs. Clutch, one ; surface dull, and having a ring round the larger end of 

 reddish -brown specks and blotches ; axis 97 to 114 mm., diameter 54 to 69. 



Incubation-period. Sixty dajs. 



Breeding-season. November to January. 



Distribution and forms. Round the Sub-antarctic Circle. Four forms have been 

 separated : T. m. melanoplirys (Temm. and Laugier) from the Cape Seas, probably 

 breeding at Gough Island, Tristan d'Acunha and the Falkland Islands ; T. m. 

 belcheri Mathews, with longer bills of paler coloration, from Kerguelen Island ; 

 T. m. impavida Mathews, with shorter bills, grey lores, and more black in front and 

 above the eyes ; and T. m. richmondi Mathews from the west coast of South 

 America with long bills, deeper than that those of the Kerguelen form, no grey 

 on the lores and the black about the eye reduced to a very faint marking. 



39. Thalassarche chrysostoma. GREY-HEADED MOLLYMAWK. 



[Diomedea chrysostoma Forster, Mem. Math. Phys. (Paris), Vol. X., p. 571, 1785 : Cape Seas. 

 Extra-limital.] 



Gould, Vol. VII., pi. 41 (pt. xxxii.), Sept. 1st, 1848. Mathews, Vol. II., pt. 3, pi. 97, Sept. 

 20th, 1912. 



Diomedea culminata Gould, Proc. Zool. Soc. (Lond.), 1843, p. 107, Dec. : " Southern, Indian 

 and South Pacific Oceans " = Cape Seas. 



Thalassogeron chrysostoma alexanderi Mathews, Austral Av. Rec., Vol. III., pt. 3, p. 55, 

 April 7th, 1916 : West Australia. 



DISTRIBUTION. Southern Australian Seas. One specimen preserved in Mathews's collection 

 and another in Perth Museum. Cf. Alexander, Emu, Vol. XIX., pt. I., p. 59, July 1st, 1919. 



Adult male. Head, hind-neck and mantle grey with white base to the feathers, 

 becoming dark brown or black on the middle of the back, scapulars and wing -coverts ; 

 lesser, median, and greater wing-coverts dark brown, with whitish bases like the 

 bastard -wing, primary-coverts and quills, the latter with white shafts and pale brown 

 inner webs ; secondaries dark brown with white on the basal portion ; olecranal 

 feathers dark brown with pale inner webs which become white at the base ; rump 

 and upper tail-coverts pure white ; tail dark hoary -grey with white shafts ; feathers 

 above and in front of the eye black ; sides of throat, face, and fore-neck white, 

 more or less washed with grey ; remainder of the under-surface white ; axillaries 

 pale grey with whitish tips ; feathers round the margin of the under-whig blackish ; 

 bill black, the culinen yellow, divided from the tip, which is horn colour, by a black 

 patch, base and lower edges of mandible yellow ; feet and legs grey, webs fleshy-pink. 

 Total length 910 mm. ; culmen 111, wing 518, tail 213, tarsus 86. 



Adult female. Similar to the adult male. 



E 2 



