GEOGRAPHICAL DISTRIBUTION. 41 



The similarity between the British and Japanese Long-tailed 

 Tits has often been remarked. They are so nearly allied that 

 some examples are very difficult to determine; nevertheless, be- 

 tween their respective ranges an apparently distinct species occurs. 

 The Continental Long-tailed Tit {Acredula caudata) is found in 

 Northern and Central Europe, and across Siberia to the island of 

 Yezzo. It can scarcely be called the arctic race of the Long-tailed 

 Tit, firstly, because it occurs in Central Europe, and secondly, be- 

 cause in Central Siberia a real arctic race oi Acredula caudata occurs. 

 There is, however, much evidence to prove that it intergrades with 

 the British Long-tailed Tit, and it may possibly do so with the 

 Japanese Long-tailed Tit. One fact is absolutely certain, that the 

 immature birds of all these races differ widely from the Siberian race, 

 and approach very near the other two races, from which it may rea- 

 sonably be assumed that it is the Siberian race which has become 

 whiter, and not the British and Japanese races which have become 

 darker. 



The existence of a pale Siberian race between a darker Eastern 

 and a datker Western race is found almost exclusively amongst resi- 

 dent birds. Migratory species either range with little or no local 

 variation across the Palsearctic Region from the British Islands to 

 Japan, or are represented by an Eastern and a Western race. Very 

 many Japanese birds belong to this category. The following British 

 birds are represented in Japan by Eastern races which are regarded as 

 only subspecifically distinct because they are connected by intermediate 

 forms : — Buteo vulgaris, Regulus cristatus, Lanius excubitor, Motacilla 

 boarula, Anthus spinoletta, Alcedo ispida, Ardea alba, Anser segetum, 

 Tringa alpina, Tringa minuta, Charadrius cantianus, Numenius 

 arquatus, Numenius phmopus, Limosa rufa, Limosa melanura, Rallus 

 aquaticus, Podiceps rubricallis, and some others. 



