20 NORTH' AMERICAN BIRDS. 



ORDER LONGIPENNES. THE LONG-WINGED 



SWIMMERS. (Page i.) 



Families. 



a 1 . Bill with the lower mandible not longer than the upper, and not excessively 



compressed. 



b l . Covering of the upper mandible composed of three distinct pieces a ter- 

 minal unguis, or hook, a lateral piece, and a cere-like piece saddled upon 

 the culmen, its edge overhanging the nostril. 



Stercorariidae. (Page 20.) 

 V. Covering of upper mandible consisting of a single piece, through which the 



nostrils are pierced Laridse. (Page 23.) 



a 2 . Bill with lower mandible much longer than the upper, both mandibles excessively 

 compressed, like a thin knife-blade, for terminal portion. 



Rynchopidae. (Page 48.) 



FAMILY STERCORARIID-^. THE SKUAS AND JAEGERS. (Page 20.) 



Genera. 



a 1 . Size large (in bulk equal to the largest gulls), and form robust ; depth of bill at 

 base equal to not less than half the length of the upper mandible, measured 

 along the side ; tarsus shorter than middle toe with claw ; tail short, nearly 

 even, the middle pair of feathers scarcely projecting beyond the rest ; color 

 dull brownish, sometimes streaked (never barred) with paler, the base of the 

 primaries with a whitish patch Megalestris. (Page 20.) 



a 2 . Size medium or rather small (not exceeding the medium-sized gulls), and form 

 more slender and graceful ; depth of bill at base less than half the length of 

 the upper mandible, measured along the side ; tarsus decidedly longer than 

 middle toe with claw ; middle rectrices in the adult projecting far beyond 

 the rest ; color plain slaty or dusky, often varied with white or yellowish, 

 in the adult, dusky barred with paler in young ; no white at base of primaries. 



Stercorarius. (Page 21.) 



GENUS MEGALESTRIS BONAPARTE. (Page 20, pi. VII., fig. 1.) 



Species. 



COMMON CHARACTERS. General color nearly uniform grayish brown or sooty, 

 usually indistinctly streaked with light rusty, or cinnamon, especially around neck 

 and on back ; quills whitish at base. Eggs olive, spotted with brown. 



