110 THE CAPERCAILLIE. 



outlet towards tlie west, the wave of advance has been forced 

 up the valley until it has reached l^eyond the limit of spruce, 

 Scotch fir, and larcli. Tlie inevitable law exists that there is 

 a distinct limit to the population of a species in any one 

 locality, regulated by the size, capabilities, and amenities of 

 the area, and when this limit is reached and exceeded the 

 surplus population is forced to seek new ground. Further, as 

 tlie internal pressure continues and increases, the greater 

 diihculties will be faced and surmounted by the pioneers, in 

 order to fulfil the destiny of the species, and the amount of 

 success acliieved will depend upon the hardihood and " fitness" 

 of the species in the struggle for existence. 



The easiest and most natural courses of advance foUow 

 the valleys, up or down stream, or stretch along the wooded 

 footliills and slopes, preferring, as already pointed out, the 

 sunny ex])osures. Tliis is clearly illustrated by the fact, that 

 Capercaillies in a comparatively short space of time reach and 

 populate more remote localities in the directions whence the 

 great valleys lead them, than they do in those directions 

 where mountainous or treeless country intervenes.^ 



The beau-ideal of a safe harbourage and permanent home 

 for tlie Capercaillie would then appear to be as follows : — 

 A forest of spruce, Scotch fir, and larch, mixed, of, say 700 to 

 1(100 acres or more in extent, having a southern exposure, or 

 lying well to the sun, of which forest certain portions — say a 



' The coinparativo rate of advance by valleys and over mountains is illus- 

 trated — to choose amongst a great mass of similar statistics — by the extreme 

 limit reached by the Tay valley route in 1877 {vide Map), and the distance 

 reached at Loch Kennord in the same year ; the former — ]\Iilngavie near Glas- 

 gow — some 45 miles in a direct line from Taymouth, and the latter only 7A. 

 Or, to select another example— the limit reache<l l)y the Tay valley route to 

 Dunkeltl, and thence l»y Strathniore into Forfar in 1865 (Brechin district- 

 over 50 miles in a direct line from Taymouth), as compared with that reached 

 in (JliMishee in the same year (Dalnaglar, only about half that distance in a 

 straight line from Taymouth). 1 am inclined to think, judging from a large 

 mass of data, that t\\f birds rarely, or only under exceptionally strong pres- 

 sure, cross mountain tracts, utUcss they can view forest-covered country beyond. 



