674 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
The Stercorariide are more predatory in their habits than the Lari- 
de being, in fact, the most predaceous of sea-fowl—veritable ‘ ‘robbers 
of the sea.” The smaller Jaegers (genus Stercorarius) 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 STERCORARIIDE. 
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 hali twisted. 
Coprotheres (p. 680). 
bb. 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 Catarractes Brisson, 1760) Briwnicu, Orn. Bor., 1764, 32. (Type,. 
by monotypy, C. skua Briinnich.) 
Cataracta (emendation) Rerzius, ed Fauna Suecica, 1800, 160. 
Cataractes (emendation) Fiemina, Philos. Zool., ii, 1822, 263.—Gray, List Gen. 
Birds, 1840, 78. 
Catarractes (emendation) Pattas, Zoogr. Rosso-Asiat., ii, 1827, 309. 
Catarrhacta (emendation) Srrickitanp, Ann. and Mag. N. H., vii, 1841, 40. 
Catarrhactes (emendation) Brucs, Journ. fiir Orn., Jan., 1853, 108. 
Megalestris BoNaPARTE, Compt. Rend., xliii, 1856, 643; Cat. Ois. d’ Eur. Parzudaki, 
1856, 11. (Type, by monotypy, Larus catarractes Linneeus=Catharacta skua 
Briinnich.) 
Buphagus Couzs (ex Moehring, 1752) Proc. Acad. Nat. Sci. Phila., 1863, 124. 
(Type, by original designation, Catharacta skua Briinnich.) : 
Very large, strongly built Stercorariide (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. 
