334 KEY A^D DESCRIPTION 



in winter (the only season the bird is seen in the United 

 States) mainly white, with a varying number of blackish marks 

 on the back and sides of head ; back and wings dark pearl-gray ; 

 under parts, except throat, white; first primary black, with the 

 inner half of the inner web white except at the tip ; the next 

 three tipped with white; the secondaries tipped with white. 

 In summer the whole head and throat are slate-colored. 



Length, loj ; wing, lOf (lOJ-Ul); tail, 4J, forked, | ; tarsus, 1^; 

 cuhnen, 1. Arctic regions; south in winter to New York, Great Lakes, 

 and Great Salt Lakes ; casual in Kansas and the Bahama Islands. 



FAMILY LXI. SKUAS AND .JAEGERS (STERCORARtlD.E) 



A small family (G si)ecies) of mainly dark-colored, rather 

 long-tailed, long-winged, swift-flying, swimming birds, with 

 the central tail feathers abruptly projecting beyond the others. 

 These birds are hawk-like in the form of their bills* 

 »V— y-,^ and in their actions ; they chase the terns and smaller 

 ^ gulls and snatch from them the fish and other prey 



' which they have caught. Although good swimmers, 



they seem unable to dive. The bill has a large, cere-like cover- 

 ing to the nostrils. 



Key to the Species 



* Wing over 15 long ; culmen over 1| ; tarsus, 2\-2\ 1. Skua. 



* Wing, 13^-15 long ; culmen under 1^; tarsus, lf-2| 



2. Pomarine Jaeger. 



* Wing not over 1.3J long ; tarsus not over 1 J ; central tail feathers acute. 



(A.) " • 



A. Scaly cere over the nostril more than half the length of the cul- 

 men ; central tail feathers projecting less than 5 inches bcj'ond 

 the others 3. Parasitic Jaeger. 



A. Scaly cere less than half the length of the culmen ; central tail 



feathers in the adult projecting over 6 beyond the dthcrs 



4. Long-tailed Jaeger. 



1. Skua (35. MegaUstris skha). — A northern, large, stout- 

 bodied, dark-brown sea-bird, with a nearly even tail having all 

 feathers broad at tip; the luider parts are somewhat lighter 

 than the upper ones, and the neck is streaked with whitish. 



