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Aut. XVIII. — Ohscrvations on the Arctic and Skua Gulls of 
British OrnlthcJogists. By the Reverend John Fleming^ 
D. D. F. K. S. Ediii. M. W. S. Communicated by the Author. 
The two species of gulls described by Linnmus^ in the 
twelfth edition of his Sy sterna Naturae, under the trivial names 
Parasiticus and Cataractes^ differ from the other birds of tlie 
genus with which they are associated, in the peculiar structure of 
their bills, and in the singularity of their manners. While the 
upper mandible in the common gulls may be regarded as simple, 
it presents a more complicated structure in the species to which 
we have now referred. In these, it consists of two pieces, the 
most remarkable of which is softer than the other, and forms a 
corneous plate, situated on the upper side, aild extending for- 
wards from the base nearly two-thirds of the whole length of 
the mandible, without being extended to the margin on eidier 
side. This plate has been compared to the cere^ or thick colour- 
ed skin, observed at the base of the biU of hawdcs and eagles, 
from which, however, it differs, in not reaching to the gape on 
each side, and in being of a firmer consistence. The nostrils 
are situated on the inferior margin of this plate, near its distal 
extremity. 
When in pursuit of food, or engaged in defending their nests, 
these birds far excel the other gulls in the rapidity of their 
flight. They live on fish, which they seldom obtain directly by 
means of their own industry. They watch attentively the ef. 
forts of the other gulls while fishing, and when they perceive 
any of these to have been successful, they instantly fly towards 
them ; and, by an unremitting pursuit, compel them reluctant- 
ly to yield the prize. Inattentive observers have mistaken the 
vomited matter for excrement, and have concluded that they 
live on the dung of their weaker neighbours. 
The other gulls are remarkable for their shyness and timidity 
at all seasons.- These, on the contrary, are bold and vigorous, 
especially during the breeding season, and will not hesitate to 
attack birds of prey, dogs, or men, when approaching their 
young. The claw of the inner toe is more arched than in the 
VOL. I. NO. T. JUNE 1819 . G 
