BIRD-ASSOCIATIONS IN SCOTLAND 53 
earliest species takes place, much in the order of arrival; 
the Whinchat, Yellow Bunting, Tree-pipit, and Whitethroat 
being steadily crowded out by the increasing density of the 
tree-canopy, and the consequent recession of the undergrowth. 
Such a crowding-out of certain species has been a striking 
and interesting feature of a certain West Lothian plantation 
with which I have been familiar for a series of years. Ina 
natural wood no such succession occurs. The wood has a 
stable character, conserved through natural seeding, and the 
avifauna is likewise stable, or at least only subject to the ebb 
and flow never entirely absent in bird-life. 
The faunal character of a wood is influenced to some 
extent—apart from its vegetative aspect—by the topography 
of the neighbourhood, and, presumably, by the climate, 
but there is little doubt that these factors, while they 
cannot be ignored, are of secondary importance. <A 
Scottish pine-wood, for instance, approaches much closer 
faunistically to a similar form of forest in the south of 
England, than it does to a deciduous wood in its own 
neighbourhood, and if this is so, it is sufficient to indicate 
the predominant influence of the plant-formation. 
In a general comparison of deciduous and coniferous 
woods it will probably be found that the deciduous has the 
richer avifauna, not necessarily so in species, but in 
population-density. Where we have the two side by side 
and conveniently comparable, this is often found to be 
the case. In the district of Rothiemurchus, for example, 
a faunal increase is at once apparent when one passes 
from the pines to the birches, the loss of certain species 
peculiar to the pine-forest being more than made good by 
a large increase in such dominant species as Chaffinch and 
Willow-wren. Of the different forms of pine-wood, Scots- 
pine is perhaps the most productive, and larch the least so. 
In the case of deciduous woods, it is probable that the 
young half-grown plantations possess a greater population 
to the acre than the full-grown natural woods; that is to 
say, the migratory fauna is relatively the richer. The 
stable types vary according to tree dominance. An oak- 
wood, with its comparatively open growth, and closer 
