326 BIRDS OF NEW ENGLAND AND EASTERN NEW YORK 



one is thoroughly familiar with their size and their different 

 plumages. 



GrEEAT BiiACK-BACKED GuLL. Lwvus mavinus 



29.00 



Ad. in summer. — Tail and under parts pure white; back and 

 wings apparently black (really dark brown) ; wings edged pos- 

 teriorly with white; bill yellow; feet pale flesh-color. Ad. in 

 winter. — Similar, but top of head and hind neck streaked with 

 dusky. Im. — Upper parts dusky, tail dusky, crossed near the tip 

 by a narrow band of brownish- white ; head, neck, and under parts 

 white, streaked and washed with brown. 



The Black-backed Gull is a winter resident along the sea- 

 coast of New York and New England. A few individuals 

 arrive in August, and a few linger till May, but the species 

 is commonest in the winter months. It is much less com- 

 mon, however, than the Herring Gull, and as a rule keeps 

 to the outer shores and beaches. Occasionally, however, one 

 or two may be observed in a harbor or even in a fresh- water 

 pond near the sea ; there are generally one or two among 

 the Herring Gulls that gather off T wharf in Boston. A 

 common cry of the Black-backed Gull is a harsh Jcyow, 

 suggesting the note of the Green Heron. 



When a large flock of gulls are standing on a flat or sand- 

 bar, the mature Black-backed Gulls will be easily distin- 

 guished from the Herring Gulls, if they stand with their 

 backs and sides toward the observer ; the black wings and 

 back will then present a striking contrast to the pure white 

 head and neck. To identify a bird when flying, one must be 

 sure to get a view of the upper part of the wings ; even a 

 Herring Gull will often appear to have dark wings, when 

 the under surface is seen in shadow. The immature Black- 

 backed Gulls can often be told from the immature Herring 

 Gulls only if the two stand side by side, when the difference 

 in size becomes apparent. 



