COMMON TERN. 17 



while occasionally they are pale olive-brown. The underlying 

 spots are purplish-grey, and are always distinct. Axis, 2-3-2-6 

 inches; diam. 1-7-1-85. 



THE TRUE TERNS. GENUS STERNA. 



Sterna^ Linn. Syst. Nat. i. p. 227 (1766). 



Type, probably S.flnviatilis (Naum). 



Like the preceding genera, the Terns have the outermost 

 tail-feathers much longer than the rest, and pointed. They 

 differ from Gelochelidon in having a short tarsus, which measures 

 less than the middle toe and claw, and in the case of the genus 

 Sterna never exceeds the latter. The tail, according to Mr. 

 Howard Saunders, is at least half, and generally more than 

 half, the length of the wing. The True Terns are also remarkable 

 for their compressed and slender bill. 



They are world-wide in their distribution, and are almost 

 exclusively maritime in their haunts. 



Intermediate between the Caspian Terns and the genus 

 Sterna is the Indian genus Seena, which has a single river- 

 haunting species, Seena seena (Sykes), remarkable for its stout 

 bill, which has the genys very short, and its long tail, which is 

 more than three-fourths the length of the wing. 



I. THE COMMON TERN. STERNA FLUVIATILIS. 



Sterna fluviatilis, Naum. Isis, 1819, pp. 1847, 1848 ; Dresser, 

 B. Eur. viii. p. 263, pi. 580 (1872) ; B. O. U. List. Brit. B. 

 p. 180 (1883); Saunders, ed. Yarrell's Brit. B. iii. p. 549 

 (1884); id. Man. Brit. B. p. 631 (1889); Lilford, Col. 

 Fig. Brit. B. part xx. (1891) ; Saunders, Cat. B. Brit. Mus. 

 xxv. p. 54 (1896). 



Sterna hirundo, Lath.; Macgill. Brit. B. v. p. 638 (1852); 

 Seebohm, Hist. Brit. B. iii. p. 280 (1885). 



Adult Males. General colour about pearl-grey, including the 

 wing-coverts and scapulars, the latter white at the ends ; rump 

 and upper tail-coverts white ; primary-coverts pearl-grey, with 

 the inner webs more dusky; primaries dark grey externally, 

 with white shafts, accompanied by a blacker border along its 

 15 C 



