674 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 



The Stercorariidse are more predatory in their habits than the Lari- 

 dse being, in fact, the most predaceous of sea-fowl — -veritable ' ' robbers 

 of the sea." The smaller Jaegers (genus Stercorarlus) pirate upon 

 gulls and other sea-fowl, thus earning the common names of "gull 

 chaser" "jaeger" (hunter), etc.; while the larger skuas (genus Megales- 

 tris) also beat along the shores or even over the land, and besides 

 forcing gulls and other birds to disgorge or relinquish their food prey 

 upon other birds, in the manner of falcons and hawks. Indeed, it is 

 said that at Kerguelen Island, in the Antarctic Ocean, the Megales- 

 tris antarcticus keeps strictly to the land, where it is very destructive 

 to ducks and other water-fowl. The nest is placed upon the ground, 

 near the sea-shore on the margin of inland lakes. The eggs are deep 

 olive-brown in color spotted with darker. 



KEY TO THE GENERA STERCORARIID^E. 



a. Larger and much more strongly built (wing 380 to more than 400 mm.); greatest 

 depth of bill equal to or greater than distance from anterior end of nostril to tip of 

 maxilla; longest primary exceeding distal secondaries by not more than half the 

 length of wing; tarsus shorter than middle toe with claw; tail shorter, the rectices 



subtruncate at tip, the middle pair projecting very slightly Megalestris(p. 674). 



aa. Smaller and more lightly built (wing not more than 370 mm., usually much less ); 

 greatest depth of bill decidedly less than distance from anterior end of nostril 

 to tip of maxilla; tarsus longer than middle toe with claw; longest primary ex- 

 ceeding distal secondaries by much more than half the length of wing; tail rela- 

 tively longer, the middle pair of rectrices elongated. 

 b. Bill deeper, its depth at base greater than its width at same point; middle pair of 

 rectrices broad throughout, rounded terminally, their distal half tmsted. 



Coprotheres (p. 680). 



hh. Bill less deep, its depth at base not greater than its width at same point; middle 



pair of rectrices tapering, acuminate, not twisted Stercorarius (p. 686). 



Genus MEGALESTRIS Bonaparte. 



Catharacta (not Catarructes Brisson, 1760) Brunnich, Orn. Bor., 1764, 32. (Type, 



by monotypy, C. skua Brunnich.) 

 Cataracta (emendation) Retzius, ed Fauna Suecica, 1800, 160. • 

 Cataractes (emendation) Fleming, Philos. Zool., ii, 1822, 263. — Gray, List Gen. 



Birds, 1840, 78. 

 Caturractes (emendation) Pallas, Zoogr. Rosso- Asiat., ii, 1827, 309. 

 Catarrhacta (emendation) Strickland, Ann. and Mag. N. H., vii, 1841, 40. 

 Calarrhacles (emendation) Bruch, Journ. fiir Orn., Jan., 1853, 108. 

 Megaleslris Bonaparte, Compt. Rend., xliii, 1856, 643; Cat. Ois. d' Eur. Parzudaki, 



1856, 11. (Type, by monotypy, Larzis catarracies Linnaeus= CafAaroc/a sAuo 



Brunnich.) 

 Buphagus Coues (ex Moehring, 1752) Proc. Acad. Nat. Sci. Phila., 1863, 124. 



(Type, by original designation, Catharacta skua Briinuich.) 



Very large, strongly built Stercorariidse (wing about 380-432 mm.) 

 with tarsus shorter than middle toe and claw, greatest depth of bill 

 equal to or greater than distance from "anterior end of nostril to tip of 

 bill, longest primary exceeding distal secondaries by not more than 

 half the length of wing, and rectrices sub-truncate at tip, the middle 

 pair projecting very slightly if at all beyond the next pair. 



