BIRD-ASSOCIATIONS IN SCOTLAND 51 
we are most likely to have an irregular and broken face 
supplying abundance of sites for the lodgment of birds. 
An ideal cliff, with abundance of turfy covering at its summit, 
and innumerable ledges and crannies below, such as occurs 
on many an island in the Hebrides, has few possible sites 
untenanted. 
At the cliff-ssummit and on the grassy shelves are the 
scattered nests of Herring and Lesser Black-backed Gulls, 
the former almost invariably the more abundant. Below, 
every ledge of size and suitability has its crowded ranks of 
Guillemots ; the narrower and isolated ledges are appropriated 
by the Kittiwake; while the deeper cracks and crevices hold 
Razorbills. Inthe bigger fissures and small caves are scattered 
nesting-sites of Shags and Black Guillemots; and in the 
caves themselves colonies of Rock-doves. From the cliff-top, 
as far down as they extend, the grassy slopes are honey- 
combed by the Puffin. There are two small Passerines, 
characteristic members of the avifauna of the sea-cliff—the 
Rock-pipit along the summit, and the Wren on the cliff itself. 
Of the rarer members of the list are Peregrine and Sea-eagle, 
the former absent from few such colonies, the latter once 
characteristic, but now nearly gone. | 
The low flat islands, lacking cliffs, possess Herring and 
Black-backed Gulls, Terns (Common or Arctic), Rock-pipit, 
Oyster-catcher, Eider-duck, and not infrequently the Mallard ; 
and, where they are of sufficient extent, the Corn-bunting 
and Twite. 
WOODLAND ASSOCIATIONS, 
The associations of this group are probably best 
arranged according to the dominant tree-character, such as 
pine, larch, beech, oak, birch, etc., but it is convenient in 
the first place to classify them into the two broader sections, 
Coniferous and Deciduous, in which the faunal distributions 
are perhaps more marked. Each section has a characteristic 
avifauna, modified in accordance with secondary type. The 
avifauna is also to some extent affected by the stage of tree- 
growth, A young growing plantation, for example, shows a 
botanical succession and an accompanying ornithological 
