BONAPARTE'S GULL. MASKED GULL. 253 



SPECIES 242 BONAPARTE'S GULL. 



Larus Bonapartii. Swainson. 

 Mouette de Bonaparte. Temrn. 



THIS rare species, whose first and only European occurrence 

 was recorded by the late William Thompson, Esq., from a 

 specimen obtained near Belfast, in February, 1848, is one of 

 great interest to the ornithologist, as it almost presents to us 

 a connecting link between the Sternidae (terns) and Xema3 

 (black -headed gulls). Found abundantly upon the shores of 

 Northern and Arctic America,* it associates with flocks of 

 terns, to which its cry has some similarity, and in such num- 

 bers, that in Chesapeake Bay seventeen were killed at one dis- 

 charge of a double-barrelled gun by a son of Mr. Audubon. 

 Habitat Northern America. 



SPECIES 243 THE MASKED GULL. 



Larus capistratus. Linn. 

 Moutte a masque brun. Temm. 



THIS species, if it be distinct from the black-headed gull, pre- 

 sents such a close affinity that the most distinguished Con- 

 tinental ornithologists are doubtful of the propriety of ad- 

 mitting its specific distinctions. 



Critically examined by Mr. Thompson, who brought for- 

 ward specimens answering to the description of the masked 

 gull, and others of the black-headed species, and described 

 their different seasonal changes in a paper read before the 

 Zoological Society of London, we must at least infer from 

 it, on account of the changes of plumage, and the difference 

 of size being so variable, that, until further knowledge is ob- 

 tained of a habitat for the species, and a sufficient number of 

 specimens all agreeing in presenting similar dimensions, with 

 other differences from varieties of the black-headed gull, we 

 must remain in doubt respecting it. 



Two of these birds came under our notice, one exposed for 

 sale in Mr. Glennon's shop, and another shot inland at Dun- 

 drum. Mr. Thompson noticed four or five birds presenting 

 a similar appearance, which have also occurred in the north 

 of Ireland. 



* Audubon. 



