APPARENT EXCEPTIONS. 189 



cealment or escape. Accordingly it is among such 

 birds almost exclusively that the law of assimila- 

 tive colouring prevails. And among them it is 

 carried to a perfection which is wonderful indeed. 

 Every ornithologist will recognise the truth of the 

 observation, that this law prevails chiefly among 

 the Grouse, the Partridges, the Plovers, the Snipes, 

 Woodcocks, Sandpipers, and other kindred fami- 

 lies, all of which inhabit open ground. There can 

 be no better examples than the Grouse and the 

 Ptarmigan of our Scottish mountains. The close 

 imitation in the plumage of these birds of the 

 general tinting and mottling of the ground on 

 which they lie and feed is apparent at a glance, 

 and is best known to those who have tried to see 

 Grouse or Ptarmigan when sitting, and when their 

 position is indicated within a few feet or a few 

 inches by the trembling nostrils and dilated eye- 

 balls of a steady Pointer-Dog. In the case of the 

 common Grouse, as the ground is nearly uniform 

 in colour throughout the year, the colouring of the 

 bird is constant also. But in the case of the 

 Ptarmigan, it changes with the changing seasons. 

 The pearly grays which in summer match so ex- 



