Larus marinns. 
Boston Harbor, Mass. 
1893. The majority of the birds (I was on a dumping scow off 
Jan. 19. the outer islands) were Herring (lulls, rather more than half 
of them young or immature. Black-baclied Gulls were very 
numerous, also. They mingled freely with the Herring Gulls 
and seemed to be on good terras with them. I counted 25 Black- 
backs in full plumage in one flock and there were many young, 
also. It was not easy to separate the latter from the young 
Herring Gulls when the two were freely intermingled on the 
ice cakes but on wing the Black-back of whatever age or plu¬ 
mage was readily distinguished by its slower, steadier wing ^ 
a strong 
beats and heavier, more direct flight. This bore^resemblance 
to the flight of the Bald Eagle. Indeed Mr. Bangs and I agreed 
that it would be a difficult matter to distinguish a young 
Black-back from a brown Eagle at any distance beyond two or 
three hundred yards, for the two are very similar in general 
appearance as well as motions. 
Cambridge, Mass. 
1899. On the morning of the 13th I saw two fine adult birds of 
December. this species floating near the middle of an immense bed of 
Herring Gulls in Fresh Pond. 
Co 
