HYDROPROtKN'E. 309 



Bill livid red in summer, reddish black in winter and in young 

 birds ; irides dark brown ; legs vermilion. 



Length 9*5 ; tail 2*8 ; wing 8 25 ; tarsus '75 ; bill from gape 1*3. 



Distribution. Temperate Europe and Asia, south of lat. 55 N., 

 in summer, Africa to Australia in winter. This Tern has not 

 been clearly identified from any part of India west of Tipperah, 

 whence a specimen was sent to Mr. Hume, but it has been several 

 times shot in Ceylon ; Gates found it common at the mouth of 

 the Sittang, in Burma, and a skin was sent from South Andaman 

 by Mr. de Koepstorff. 



Genus HYDROPROGNE, Kaup, 1829. 



This is a genus of Terns distinguished by its stout and long 

 beak and legs, and by its very short tail, only about one-third the 

 length of the wing. 



There is only a single species, which is the largest Tern known. 



1498. Hydroprcgne caspia. The Caspian Tern. 

 Sterna caspia. Pall. Nov. Comm. Petrop. xiv, i, p. 582, tab. xxii, 



B. B. p. 427 ; Barnes, Birds Bom. p. 428 ; Oates in Humes N. $ E. 



2nd ed. iii, p. 295. 

 Hydroprogne caspia, Kaup, Nat'drl. Syst. pp. 91, 196; Saunders, 



Cat. B. M. xxv, p. 32. 

 Sylochelidon caspius, Brehm, Vb'g. Deutschl. p. 770 ; Blytli, Cat. 



p. 290 ; Jerdon, B. I. iii, p. 835 ; King, J. A. 8. B. xxxvii, pt. 2, 



p. 218 ; Holdsworth, P. Z. S. 1872, p. 480 ; Hume, S. F. iv, 



p. 414. 



The Largest Tern, Jerdon ; Kekra, Sind. 



Fig. 71. Head of H. caspia. \. 



Coloration. In summer plumage the forehead, crown, nape, and 

 sides of head to below the eye black glossed with dark green ; 

 remainder of upper plumage, with wings, pearl-grey ; the inner 

 webs of the primaries (and the outer webs, when the frosted 

 surface has worn off) darker ; rump and tail still paler ; lower 

 plumage with sides, and sometimes back, of neck, cheeks, and 

 lower iores pure white. 



