BONAPARTE S GULL. 



727 



Key to species of genus Larus. 

 (Adults in breeding plumage.) 



, /Head black or brown 2 



\ Head white 6 



« /Under wing -coverts all white ... 3 

 \ Under wing-coverts slate-grey ... 5 



o /Wing over 400 mm L. ichthyaetus, p. 741 



\ Wing under 400 mm 4 



. /Bill red, tip of wing white L. melanocephalus, p. 738 



\Bill black, tip of wing black L. Philadelphia, p. 727 



f Head black, first developed primary grey with 



k J white tip L. minutus, p. 730 



) Head coffee-brown, first developed primary 



[_ largely white with black tip .... L. ridibundus, p. 733 



f First developed primary white or chiefly white 7 

 6^ First developed primary chiefly black or 



[_ blackish 8 



-/Larger, bill 53-70 mm L. hyperboreus, p. 765 



\ Smaller, bill 40-50 mm L. glaucoides p. 769 



f Bill greenish-grey to greenish -yellow, tip only 



8<( yellow L. canus, p. 744 



[_ Bill yellow with red spot near gonys . 9 

 "Tip of wing 5-8 cm. pure white, bill very large, 



at gonys 22-27 mm. high .... L. marinus, p. 761 



Tip of wing black with white spots . .10 

 f Generally larger, back bluish-grey . . . L. argentatus, p. 748 



10 <j Generally smaller, back slate-grey or slate- 



(_ black L. fuscus, p. 756 



LARUS PHILADELPHIA 



446. Larus Philadelphia (Ord)— BONAPARTE'S GULL. 



Sterna Philadelphia Ord, in Guthrie's Geogr., 2nd Amer. ed., p. 319 



(1815— near Philadelphia, U.S.A.). 



Larus Philadelphia (Ord), Yarrell, in, p. 584 ; Saunders, p. 661. 



Description. — Adult male and female. Winter. — Fore-head white ; 

 crown white with mixture of dark grey on back of crown and a 

 small spot in front of eye and large one on hinder ear-coverts ; 

 back of neck ash-grey ; mantle, scapulars, and back blue-grey ; 

 lower-rump, upper tail-coverts, whole under-parts and tail white 

 (under-parts stated to have often a rosy tinge in life) ; primaries : 

 2nd (outer) white inner web and shaft, black outer web and tip, 

 3rd same but black tip longer and extending for a short distance 

 down inner edge of inner web (outer web white but sometimes with 

 varying width of black edging on distal half), 4th same but inner 

 part of inner web grey and a small white spot at apex of black tip 

 which extends in a short, narrow edging down both webs, 5th as 

 last but white spot at apex slightly larger and whole of inner web 

 grey, 6th as 5th, but both webs grey and shaft greyish, 7th blue- 

 grey, black at tip restricted and extreme tip grey, 8th blue-grey 

 shaft dark grey, tip of inner web edged black (sometimes sub- 



