GULLS. 47 
Though most of the species are truly marine, they often wander far 
inland, and many breed in large colonies in the proximity of fresh 
water. 
Family I. Stercorartipa. Skvuas. 
On the floor of this Case will be found the Skuas or Parasitic Gulls, 
mostly birds of a dusky or reddish-brown colour, and remarkable not 
only in possessing a “ cere”’ or bare wax-like base to the bill, but also as 
regards their habits. Though apparently well adapted both for swim- 
ming and diving, they rather avoid the water, and obtain their food by 
destroying other birds or by robbing them of their prey. 
Four species of the Great Skuas (Megalestris) are known, of which 
one, the “ Bonxie” (M. catarrhactes) (409), from the North Atlantic, 
breeds in the Shetland Islands. One of the Southern forms (M1. ant- 
arctica) (410), ranging from New Zealand to the Falkland Islands, 
appears to feed almost entirely on Petrels, and closely resembles some 
large hawk as it rapidly quarters the hill-sides in search of prey. Of 
the smaller long-tailed species (Stercorarius), Richardson’s Skua 
(S. crepidatus) (411) has both dark and light phases of plumage, and 
nests in some of the islands off the north of Scotland; while Buffon’s 
and the Pomatorhine Skuas (S. parasiticus (412) and S. pomatorhinus 
(413)) are both winter visitors to our coasts. All three breed in 
the high north and wander far south in winter. Their habits are very 
similar; they single out a Gull, Tern or Gannet well-stocked with recently 
caught fish, and after a hot pursuit force it to disgorge part of its booty, 
which is seized ere it reaches the water, 
Family II]. Laripm. Guts anp Terns. (Plates VI., VII.) 
The Gulls may generally be distinguished from the ‘Terns by their 
strong, curved bill and square tail. Many of the larger species are 
almost omnivorous, feeding on small mammals, young birds, eggs, and 
all sorts of carrion, besides fish. They may be divided into two groups, 
those with a hood and those without. To the latter belong the Kitti- 
wakes (Rissa), with the hind toe rudimentary or absent, of which R, 
tridactyla (414) is a common British species, and a number of the larger 
species of Larus such as the Common Gull (L. canus) (425), the Herring- 
Gull (L. argentatus) (424) | Pl. VI.], the Greater and Lesser Black-backed 
Gulls (LZ. marinus (421) and L. fuscus (423)), all of which breed in the 
British Isles ; while the Glaucous and Iceland Gulls (ZL. glaucus (420), 
L. leucepterus (419)), and the Ivory Gull (Pagophila eburnea) (416) are 
occasional visitors to our coasts. Besides these a number of less familiar 
[Case 26. ] 
[Cases 
25, 26.) 
[Case 25, ] 
