NON-INDIGENOUS BRITISH BIRDS. 293 



Family LARID.^. Genus Larus. 



Sub-family LARINyE. 



BONAPARTE'S GULL. 



Larus Philadelphia, Ord. 



(British : Very rare abnormal winter and spring migrant.) 



Single Brooded. Laying season, June, and first half of July. 



Breeding area : Northern Nearctic region. Bona- 

 parte's Gull breeds in the sub-arctic regions of America, 

 from Alaska in the west to Labrador in the east. It 

 appears not to breed anywhere much above the Arctic 

 Circle, and as far south as Manitoba, presuming that the 

 species was correctly identified by Mr. Raine, who visited 

 colonies on Crescent Lake and elsewhere in this resfion. 



Breeding habits : Bonaparte's Gull is a migratory 

 bird, and reaches its breeding grounds in May. It is 

 very gregarious, and breeds in colonies of varying size, the 

 birds apparently returning to certain places every year. 

 There can be little doubt that this bird pairs for life. 

 The breeding grounds of this Gull are near lakes and 

 pools, especially such as are close to trees and bushes, 

 and on the margins of prairie lakes and sloughs. The 

 most interesting feature in the nidification of Bonaparte's 

 Gull is the fact of the birds nesting in bushes and trees. 

 This, however, is not a universal practice, and in districts 

 where such sites cannot be got, they breed in marshes on 

 the ground, as for instance on the margins of the lakes 

 on the prairies, or on low sandy islands in those lakes. 

 In the latter situations the nest of this Gull is merely a 

 shallow cavity in the sand, lined with a little dry grass. 

 The nest in a tree or a bush is a much more substantial 

 structure. When in a tree it is usually made on a flat 

 horizontal branch at some distance from the trunk. 



