20 LONGIPENNES: Long-winged Swimmers 



GLAUCOUS-WINGED GULL 



(44. Larus glaucescens) 24-27 in. 



A large Gull, with no black in any stage of plumage. 



First winter: All gray, darker below; bill black. From this a 

 gradual change brings adult plumage in the fourth spring. 



Adult: Body snow white; mantle pearly gray; primaries gray 

 with white tips; in winter, neck and head are dusky-clouded 

 above, this clouding being lost in early spring. Bill yellow. 



First winter birds are conspicuously " chunky." 



BONAPARTE GULL 



(60. Larus Philadelphia) 14 in. 



Adult: Head black, a white spot above and below eye; mantle 

 pearl gray; wing-tips all black; body white; bill slender, black. 

 Winter: Head white with dusky ear-spot and dusky wash on 

 nape. Black head is acquired in April. 



Immature: Like winter adult, but with much brown on bend 

 of wing and shoulders, and tail dusky-tipped. 



Adult stage reached at the end of two years. 



Feeds mostly in or near the surf. 



SABINE GULL See Appendix. 



(62. Xema sabini) 13 in. 



FRANKLIN GULL See Appendix. 



(59. Larus franklini) 14j in. 



CASPIAN TERN 



(64. Sterna caspia imperator) 21 in. 



Adult: Mantle pearly; cap black; bill large, dark red; tail 

 forked; primaries frosty black, very conspicuous in flight, when, 

 except for the long, pointed wing, the bird might be mistaken 

 for a Gull. Cap white-streaked in winter. 



Immature: Tail and wings marked with dusky; crown mostly 

 white, darkening to nearly black nape. 



Largest of the Terns. In size and disposition, the king of its 

 tribe. 



