WHITE-TAILED TROPIC BIRD. 79 



Genus LEPTOPHAETHON. 



Leptophaethon Mathews, Austral Av. Rec., Vol. II., pts. 2 and 3, p. 56, Oct. 23rd, 1913. 

 Type (by original designation) : Phaethon lepturus dorothece Mathews. 



Lepturus Reichenbach, Nat. Syst. Vogel, p. vn., 1852 (? 1853). Type (by original designa- 

 tion) : L. edwardsii Reichenbach = Phaethon lepturus Daudin. 

 Not Brisson, Ornith., Vol. VI., p. 479, 1760, nor Swainson 1838. 



Small Phaethons with strong bills, long wings, long tail, small legs and feet. 

 In general features the species of this genus agree with Scceophaethon, but they 

 differ appreciably in size. Proportionately the wing and tail are much longer, the 

 tail being differently formed. 



In Scceophaethon the culmen is more than half the length of the tail without the 

 central pair of tail-feathers, which is less than one-third the length of the wing. In 

 Leptophaethon the culmen is less than half the length of the tail as above, which is 

 more than one-third the length of the wing. The central tail-feathers in Lepto- 

 phaethon are very long with the webs normal and fairly wide, and the pair next to 

 the central pair are long and are twice the length of the oustide pair, the tail being 

 thus strongly wedge shaped. In Scceophaethon the central pair are very long, but 

 the webs are degenerate and are scarcely broader than the shaft, while the tail 

 otherwise is wedge shaped but without much gradation. The metatarsus is less 

 than a quarter of the length of the tail in Leptophaethon, while in Scceophaethon it is 

 more than one-third. The middle toe is never pectinate in this family. 



57. Leptophaethon lepturus. WHITE-TAILED TROPIC BIRD. 



[Phaeton lepturus Daudin, in Hist. Nat. Buffon, ed. Didot, Quadr., Vol. XIV., p. 319 (1799 =] 

 Oct. 1802 : He de France = Mauritius. Extra-limital.] 



Mathews, Vol. IV., pt. 3, pi. 232, June 23rd, 1915. 



Phaethon lepturus dorothece Mathews, Austral Av. Rec., Vol. II., pt. 1, p. 7, Aug. 2nd, 1913: 

 Queensland. 



DISTRIBUTION. Queensland, breeding on Fiji Islands (?) 



Adult male. General colour above and below pearl-white ; a circular black line 

 in front and over the eye which broadens out behind the latter ; the feathers of the 

 hinder crown and nape have dark bases ; median upper wing -coverts black ; primary- 

 quills black on the outer web and, including the shafts, white at the tips, the black 

 decreasing on the inner ones which have only a black shaft ; outer secondaries white, 

 inner ones black and white ; scapulars white, subterminally black with white edges ; 

 rump and upper tail-coverts white with black bases and black shafts ; tail-feathers 

 white with black shafts ; feathers on the sides of the rump black with white margins. 

 Bill red ; eyes white ; feet black ; tibia yellowish. Total length 400 mm. ; culmen 

 44, wing 281, tail 115, middle feathers 380, tarsus 24. 



Adult female. Similar to the adult male. 



Immature and Nestling. Not described. 



Nest. A hole or hollow of a rock or tree stump. 



Eggs. Clutch, one ; ground-colour buff ; freckled all over with purplish -brown ; 

 axis 57 mm., diameter 44. 



Distribution and forms. Throughout the oceans within the tropics, breeding 

 on isolated islets. Three forms were recognised by Mathews in 1913, and no amend- 

 ment of consequence has since been provided, thus : L. I. lepturus (Daudin) from the 

 Indian Ocean breeding at Mauritius and Rodriguez ; L. I. dorothece (Mathews) from 

 the East Australian Seas and the Pacific Ocean, in its smaller size throughout ; 

 average : culmen 45, wing 258, tail 105 mm. ; average of typical birds : culmen 50, 



