16 
BONAPARTE’S GULL. 
their wings more sedately. I found the adult birds in moult in August. 
Although their notes are different from those of all our other species, being 
shriller and more frequent, I am unable to represent them intelligibly 
by words. 
Since I began to study the habits of Gulls, and observe their changes of 
plumage, whether at the approach of the love season, or in autumn, I have 
thought that the dark tint of their hoods was in the first instance caused by 
the extremities of the feathers then gradually changing from white to black 
or brown, without the actual renewal of the feathers themselves, as happens 
in some species of land-birds. At Eastport, I had frequent opportunities of 
seeing the black-hooded males copulating with the brown-hooded females, so 
that the colour of the head in the summer season is really distinctive of the 
sexes. I found in London a pair of these birds, of which the sexes were 
distinguished by the colour of the head, and which had been brought from 
Greenland. They were forwarded by me to the Earl of Derby, in whose 
aviaries they are probably still to be seen. 
This is certainly the species described in the Fauna Boreali-Americana 
under the same name ; but it is there stated that the females agree precisely 
with the males, their hood being therefore “ greyish-black which I have 
never found to be the case. As to the Larus capistratus of Bonaparte’s 
Synopsis, I have nowhere met with a Brown-headed Gull having the tail 
“ sub-emarginate and I infer that the bird described by him under that 
name is merely the female of the present species. 
Brown-masked Gull, Larus capistratus , Bonap. Amer. Orn., vol. iv. Female. 
Larus capistratus, Bonap. Syn., p. 358. 
Larus Bonap artii, Bonapartian Gull , Swains, and Rich. F. Bor. Amer., vol. ii. p. 425. 
Bonapartian Gull, Nutt. Man., vol. ii. p. 294. 
Bonapartian Gull, Larus Bonapartii, Aud. Orn. Biog., vol. iv. p. 212. 
Adult, 14i, 32J. 
Extremely abundant in winter, on the coast of Florida. Equally plentiful 
in spring, along the coasts of the Middle and Eastern Districts, especially 
in the Chesapeake. Breeds from the Bay of Fundyto high latitudes. Not 
uncommon in autumn, on the Great Lakes, and the Ohio and Mississippi. 
Adult Male in spring- plumage. 
Bill shorter than the fiead, nearly straight, slender, compressed. Upper 
mandible with its dorsal line straight to the middle, then curved and 
declinate, the ridge narrow, the sides slightly convex, the edges sharp and a 
little inflected, the tips narrow but rather obtusfi, with a slight notch on each 
side. N asal groove rather long and narrow ; nostrils in its fore part, 
longitudinal, sub-medial, linear, pervious. Lower mandible with a slight 
