BIRD-ASSOCIATIONS IN SCOTLAND 15 
of which in turn requires sub-division according to secondary 
types: 1, Alpine and Sub-alpine Associations ; 2, Moorland 
Associations; 3, Associations of the Drainage-system ; 
4, Maritime Associations; 5, Woodland Associations ; 
6, Associations of Hill Pasture; 7, Associations of Arable 
Land; 8, Associations of Buildings. It would be impossible 
within reasonable limits to do more than survey very 
rapidly and on broad lines some of the principal and striking 
Associations contained within these groups, even had I 
knowledge sufficient to go into detail, and this I am far from 
claiming. 
ALPINE AND SUB-ALPINE ASSOCIATIONS. 
The area which I include under this heading divides 
itself naturally as follows: 1, the barren and stony region 
of the mountain-top beyond the normal limits of heather- 
growth; 2, the heather-clad hill-side; 3, the cliffs; 4, the 
_ lower slopes of detritus with a vegetative covering of grasses 
and bracken; and, finally, the alluvial area of the valley- 
bottom. These successive regions, vegetatively distinct, are 
accompanied by equally definite faunal types. In the first 
region, that of the barren ground above the heather-limit, with 
its typical stunted vegetation and frost-splintered debris, we 
have a very definite, if small, bird-association, which comprises 
the Ptarmigan, Dotterel and Snow-bunting. The first-named, 
usually the dominant species, exists all over the region, above 
an approximate altitude of some 2500 feet. The Dotterel’s 
nesting-ground is essentially limited to those areas on which 
grow the characteristic extensive mats of the alpine moss, 
Rhacomitrium lanuginosum. The third member of the 
association, the Snow-bunting, is dependent on the granite 
screes of the central mountain-tops or the similar screes 
of the Torridon sandstone and the Cambrian quartzite of the 
North-West Highlands. 
In the heather region, which follows next in order as we 
descend, the place of the Ptarmigan is taken by the Red 
Grouse, the Snow-bunting is replaced by the Wheatear, 
and the Meadow-pipit is much in evidence, to mention only 
the more typical representatives. 
