490 LESTRIS POMARINUS. 



It seems to feed chiefly, if not entirely, at the expense of 

 the smaller Gulls, which it causes to disgorge their newly- 

 obtained food, to be caught in its descent. Its flight is 

 extremely rapid, ordinarily performed by rather quiet flaps 

 of its long wings, but, in pursuit, by various movements, in 

 the manner of a Hawk. It has not been seen to prey upon 

 birds of any kind, nor even to strike with its wings or other- 

 wise those which it chases for the contents of their gullet. 

 Mr. Audubon saw it, in stormy weather, eat the fishes that 

 had been cast ashore ; and Dr. Richardson states that, in 

 the arctic seas and northern inlets of Hudson's Bay, w'here 

 it is not uncommon, it subsists on putrid fish and other 

 animal substances thrown up by the sea, as well as on the 

 matter Avhich the Gulls disgorge when pursued by it. 



Young. — The young, in their first autumn, difier from 

 the adult in more respects than in colouring. The tarsi are 

 covered on the sides and behind with thin flat hexagonal 

 scales ; whereas in the adult, the scales on the sides are 

 convex, like tubercles, and those behind conical. The 

 middle tail-feathers are but slightly longer, and the feathers 

 of the neck are of ordinary texture. The bill is much 

 smaller, bluish-grey, Avith the tip blackish ; the tarsi greyish- 

 yellow, dusky for a short space above, and on the outer side 

 below ; toes and membranes blackish. The head and hind- 

 neck greyish-brown, the feathers faintly margined with pale 

 brown. The upper parts are dark brown, the feathers faintly- 

 margined with pale brown, the larger having two sub-ter- 

 minal marginal spots. Quills and tail-feathers brownish- 

 black, with their bases, a great part of the inner webs, and 

 the shafts to near the end, white. Upper tail-coverts dark 

 brown, with four or five bars of light brownish-red. Lower 

 parts barred with dull yellowish-grey and greyish-brown, 

 more conspicuously the abdominal feathers and lower tail- 

 coverts ; axillar feathers and lower wing-coverts barred dusky 

 brown and white. The concealed part of the plumage white 

 on the loAver, greyish-white on the upper parts. The feet 

 differently coloured in some individuals. 



Length 19 inches ; extent of wings 45 ; wing from flexure 



