84 BIRDS. 
353. Rissa tridactyla (Z.). Kittiwake. 
Resident, breeding abundantly in the Flamborough range of 
cliffs. Many retire south in autumn, though the species 
is common on the coast in winter. 
Sub-fam. STERCORARITNA. 
354. Stercorarius catarrhactes (Z.). Common» Skua. 
Periodical visitant, occurring off the coast in autumn, and 
most frequently off Flamborough Head; comparatively 
rare elsewhere. ‘There is one record of its occurrence in 
the spring, at Flamborough, on the rst of March, 1868. 
Has once been obtained inland, at York, 8th Oct., 1879. 
355. Stercorarius pomatorhinus (Zemm.). Pomatorhine 
Skua. 
Periodical visitant, occurring off the coast in autumn. In 
most years only one or two—in immature plumage—are 
observed, principally at Flamborough. In October, 1879, 
an irruption of considerable extent took place, both adults 
and immature birds being extremely numerous on the 
coast, and some were shot very far inland. Before the 
date of this irruption, adult birds had been almost unknown 
in the county. 
356. Stercorarius crepidatus (Banks). Richardson’s 
kua. 
Periodical visitant to the coast, in autumn, when it is numerous 
off Flamborough, chiefly immature, old birds being un- 
common. ‘This species was extremely abundant with its 
congeners in the great flight of 1879. Has occasionally 
occurred as a straggler inland. 
357. Stercorarius parasiticus (Z.). Buffon’s Skua. 
Casual visitant in autumn, very much less frequent than S. 
pomatorhinus and S. crepidatus, and although many— 
mature and immature—were obtained during the memor- 
able irruption of 1879, it was much less numerous than 
they, and until then immature specimens only had been 
obtained. Inland, one occurred at Strensall Common on 
the 8th of October, 1879. 
