BIRDS OF NEW YORK IIQ 



that the tail feathers are abotit three inches shorter than the dimensions 

 given bv Swainson and Richardson. There seems no doubt also that the 

 specimens from Gowanus bay [Birds of L. I. p. 365] may be the yotmg of 

 the Parasitic jaeger. The specimen to which he refers as L e s t r i s 

 r i c h a r (1 s o n i [p. 367] is a Parasitic jaeger in the dark phase; thus it 

 appears that none cf Giraud's specimens can be referred with certainty to 

 the species longicaudus, although he himself refers two to that species. 

 DeKay's Lest r is richardsoni is undoubtedly a Parasitic jaeger. 

 His L . b u f f o n i is probably the same species, although it maj- be the 

 inteniiediate phase of longicaudus. 



FamUy LARIDAE 



Gulls and Terns 



Gulls and terns are distinguished by the structure of their bills, which 

 are more or less epignathous and somew^hat compressed, with a protuberant 

 gonys, but lacking the homy saddle of the jaegers. The nostrils are linear 

 or oblong, placed tow-ard the middle or in the basal half of the bill, and are 

 open transversely. Among the gulb, especially the larger sj:iecies, the 

 bill is stout, and hooked near the end, and the short s\Tiiphysis of the 

 branches of the lower mandible makes a prominent gonys, or angle of the 

 jaw. There is a continuous graduation in the size and shape of the bill 

 from the heavy hooked beak of the Great black -backed gull, to the slender, 

 nearly straight bill of Bonaparte and Sabine gulls; and among the terns 

 from the ponderous beak of the Caspian tern and the gull-like beak of 

 Gelochelidon to the slim and delicate bill of the Black tem. The tail is 

 nearly square in most gulls; in terns and some gulls it is forked. The 

 legs are short, especialh' in terns, the tibiae being bare for a short dis- 

 tance. The ,legs are placed near the center of the body, so that they 

 stand and walk with ease, carrying the body in a nearly horizontal posi- 

 tion. The plumage is long and dense on the breast so that the\- rest 

 lightly on the water, "swimming high" in comparison to divers or even 

 ducks. Gulls and terns are very uniform in coloration, being mostly white 

 with a darker mantle over the back and wing coverts, which ranges 

 from slaty black in marinus to pale pearl-gray in hyperboreus, 

 but is pure white in the Ivory gull. They have dusk}- or black 

 markings, of greater or less extent, on the primaries, excepting in 

 hyperboreus, leucopterus etc., where they are nearly pure 

 white. A great point is made of these markings in the determination of 

 species [see pi. 5, 6]. The molt occurs twice a year so that there is a slight 

 difference between the summer and winter plumages. Immature birds 



