lOO MEMOIRS OF THE NUTTALL ORNITHOLOGICAL CLUB. 



2 1 [60] Larus Philadelphia (Ord). 

 Bonaparte's Gull. 



Common transient visitor; (winter?); March 10 to June 3; July 27 to 

 November 3. 



Like many sea birds, tlie Bonaparte's Gull is much more common in the 

 autumn than in the spring migrations. It is possible that a few may occasion- 

 ally pass the winter here, as on January ist, 1905, in Lynn Harbor, Mr. F. H. 

 Allen saw among some Herring Gulls a small Gull probably of this species. 



In flight and action, the Bonaparte's Gull resembles more closely the Terns 

 than the Gulls, flitting about close to the edge of the waves and frequently drop- 

 ping down to the water. It delights in feeding in the shallow water on the 

 beaches inside of the surf line, sometimes walking, sometimes swimming, as the 

 waves recede or advance. It is a tame bird and its confiding nature makes it 

 very attractive. Occasionally it emits a harsh, rasping cry, but as a rule it is 

 silent. 



The black-headed adults in nuptial plumage are rarely seen on the Essex 

 County coast, for most of the birds in the late summer and autumn are either 

 young or adults in winter plumage. This latter plumage appears to be assumed 

 before the middle of August. The only black-headed birds I have seen in the 

 autumn were two on July 27th, 1903. I have seen birds in the winter or imma- 

 ture plumage as late as June 3d. 



The spot on the side of the head can be seen in the immature birds as well 

 as their brownish gray lesser wing coverts and the broad dark tip to the tail. 

 It is to be remembered, however, that the immature of all of our Gulls have this 

 tip to the tail. 



The distinction between immature Kittiwakes and immature Bonaparte's 

 Gulls is perhaps the most difficult. Both have a dark spot on the sides of the 

 head, but the markings on the wings when seen from above tell the story. In 

 the Kittiwake there is a white posterior margin and black anterior margin, and 

 this with the black line formed by the lesser coverts and part of the tertials 

 makes a very striking pattern. In the immature Bonaparte's Gull there is a 

 black posterior as well as a black anterior margin to the wing. 



The small size of the Bonaparte's Gull, the smallest of our Gulls, its tern- 

 like flight as well as its confiding ways, generally serve to distinguish it. 



