RED-TAILED TROPIC BIRD. 81 



Adult female. Similar to the adult male. 



Immature. The feathers of the head black with broad white tips, giving a 

 scalloped appearance ; the fore-head white, a square black spot in front and round 

 the eye ; the feathers of the back of the head, neck, sides of neck, mantle, rump 

 and upper tail-coverts barred brownish -black and white, a white tip and three bars, 

 shorter feathers with two bars only ; axillaries similarly barred ; and lesser wing- 

 coverts with bars as also scapulars ; primaries white with black shaft and black line 

 alongside, developing into an elongate spot on second and third primaries and 

 decreasing on fourth and fifth so that spot alone is seen ; the primary-coverts are 

 similarly marked ; secondaries and secondary coverts pure pinkish -white as are 

 the major coverts ; the tertials almost all black with a white border, the outermost 

 two showing semi-barring indicating method of evolution of white feathers ; all the 

 inside of the wing pure pinkish-white as all the under-surface including the under-tail 

 coverts, but a few flank feathers are obsoletely barred ; the tail is wedge shaped with 

 a slight attenuation of the central feathers which show black tips ; the other tail- 

 feathers have three spots on outer webs, remnants of bars, otherwise all white with 

 black shafts. Bill black; eyes brown; feet yellowish -white and black. 



A bird a little older has the tail white and the axillaries white and the markings 

 less pronounced, the bill showing pale brownish. 



Nestling. Covered with whitish or greyish down. 



Nest. A depression in the sand, placed under a shelving rock. 



Eggs. Clutch, one ; reddish-white covered more at the top end with purplish- 

 black streaks and brownish-red spots and blotches ; or covered similarly all over ; 

 axis 68-70 mm., diameter 48-49. 



Breeding-season. July. (Raine Island.) November, December and January. 

 (Kermadec, Lord Howe and Norfolk Islands.) 



Distribution and forms. Confined to the Indian and Pacific Oceans, breeding 

 on isolated islets. Six subspecies were recognised by Mathews in 1915, as follows : 

 S. r. rubricauda (Boddaert) from Mauritius ; S. r. westralis Mathews, from West 

 Australia and Christmas Island, Indian Ocean, with a rosier coloration, smaller bill 

 and longer wing, bill 68 against 76-80 mm. and wing 347 versus 320-336 mm. ; 8. r. 

 novcehollandice Brandt from the Kermadecs, Lord Howe and Norfolk Islands, and 

 Raine Island with a deep rose coloration with a heavier bill and longer wing than 

 typical form ; S. r. melanorhynchus (Gmelin) from Turtle, Palmerston and Society 

 Islands, differing in lacking the rose colouring ; 8. r. rothschildi Mathews from Laysan 

 and Niihau with a shorter, weaker bill, shorter wing and pure white coloration ; and 

 8. r. brevirostris Mathews from the Bonin Islands, with a very short bill 56-59 mm. 

 only, and whiter coloration. 



SUBORDER LABIFORMES. 



Four families of web-footed seabirds constitute this suborder, of which the 

 most peculiar, the Rynchopidae, does not occur in Australia, being represented in 

 Tropical America, Africa and India by distinct but very closely related species. 

 The other three have somewhat peculiar distribution each in a different manner ; 

 thus, the Sternidse include two groups which will probably later claim family rank, 

 viz., the Terns and the Noddies. Externally they differ, but from the recorded 

 anatomical items they show even more marked internal differences but as yet little 

 research has been done in this direction. Together they have somewhat delicate 

 pointed bills, delicate bodies, very long wings, generally very long forked tails and 

 small legs and webbed feet, the webbing varying in degree. The Noddies are 

 separable by their heavier bills, stouter build, shorter wings, though still long, 

 broader double-forked tails and stouter legs with fully webbed toes. The Laridae 

 are distinguished by their differently formed heavier, somewhat hooked, bills, much 

 heavier build, shorter wings, shorter square (a couple of species have semi -forked) 



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