84 JOTTINGS ABOUT BIRDS. 



warm pluvial regions the brown in the plumage is 

 intensified ; in the dry and sandy areas it is very 

 perceptibly lighter; in the Arctic regions of Siberia 

 it is of variable degrees of paleness, in obedience 

 to intensity of climate; whilst in Kamtschatka it 

 becomes bleached into almost white. All these 

 various forms of Marsh Titmouse insensibly inter- 

 grade, probably as much in obedience to the 

 gradual variation of climate as to the interbreed- 

 ing of individuals. The Hazel Grouse (Tetrao 

 bonasia), although not a British species, furnishes 

 such a remarkable instance of colour variation 

 correlated with climate, that I cannot resist de- 

 scribing it. The range of this Grouse is a very 

 extensive one, reaching from Western Europe to 

 the Pacific coasts of Asia and to Japan. The 

 individuals of this species that dwell in the dry 

 Arctic climate of the northern districts are ex- 

 ceptionally gray in colour, whilst those that inhabit 

 the mountains of South Europe, the Amoor valley, 

 and Japan (pluvial climates), are notable for their 

 rufous tints. In the Arctic climate of the north we 

 find the brown has become bleached into gray, 

 whilst the greater rainfall and warmth of the south 

 have intensified it into chestnut. 



The modifying influences of climate are also very 



