224 WILD LIFE OF SCOTLAND 



Crosses among other members of the same group, 

 whose modes of life bring them into closer contact ; 

 for instance the grouse of the heather, and the 

 blackcock of the bracken; or the blackcock and 

 capercaillie of the same fir-wood, are much more 

 frequent. 



Of the crosses which do occur, it is safe to 

 assume that the large majority escape observation, 

 and all are speedily obliterated by the ordinary 

 natural checks. Of a supposed cross between the 

 red grouse and the ptarmigan, whose areas overlap 

 still less than those of grouse and partridge, the 

 ptarmigan being perhaps the most perfectly isolated 

 of all our game birds, Professor Newman says : 

 " Information received from other quarters, induces 

 me to believe that other examples have before now 

 occurred." 



It is conceivable that just as favourite shelter 

 and diet tend to limit each variety to the place 

 where these exist, so certain tendencies, such as the 

 preference of the female for one of its own kind, 

 prevent such frequent intercrossing as would tend 

 to confusion. The relations of the game birds seem 

 to be of this intermediate character; and the 

 differences among them neither so marked as those 

 which separate the plovers, nor so loose as those 



