PARID^:. 



93 





THE LONG-TAILED TITMOUSE. 



AcREDULA CAUDATA (Linnceus). 



The Long-tailed Titmouse is one of those species which exhibit 

 a strong tendency to variation under climatic or other conditions ; 

 and ornithologists must exercise their individual discretion in classing 

 each form as a race, a sub-species, or a completely segregated 

 species. In the bird found in Scandinavia, Northern Germany, 

 Austria and Russia — extending across Siberia to Japan — when fully 

 adult the head is white ; the purity and extent of that colour 

 attaining their maximum in the far north. This is the true 

 A. caudata, as restricted by some authors ; an example of which 

 has been obtained in Northumberland, while others, as well as 

 various intergradations between this and the next form, have been 

 observed. In the Netherlands, Germany west of Cassel, and part 

 of France, it meets and interbreeds with the form which represents it 

 in the British Islands, distinguished by its duller tints and by having 

 the white on the head restricted to the crown. If separated specifi- 

 cally, this is A. rosea. In the south of France and the north of 

 Italy, this latter form meets and intergrades with the greyer-backed 

 A. irbii, which becomes the representative form in Sicily and Spain. 

 Although it is difficult to separate any but adult examples of these 



