GEOGKAPHICAL DISTRIBUTION. 39 



China, where the colour of the underparts resembles exactly that of 

 birds of Western Europe and Algeria. The young in first plumage 

 of the European race closely resemble their parents, but those of the 

 Central-Siberian race closely resemble the adults of the Baltic and 

 Amoor races, leading to the supposition that the Central- Siberian 

 race is the one -which has changed most recently. 



The Kamtschatkan race of the Nuthatch resembles the Central- 

 Siberian race in the whiteness of its underparts, but is paler on the 

 upper parts, especially on the forehead. 



These climatic variations correspond to a remarkable degree with 

 the July Isothermal Lines. The palest race (from Kamtschatka) 

 moults in a mean temperature of 54° to 58° ; the Central-Siberian 

 race enjoys a mean temperature at that season of 58° to 62°. The 

 Western race in the Baltic Provinces, which is scarcely distinguish- 

 able from the Eastern race in the valley of the Amoor, moults in a 

 mean temperature of 65° to 70° ; whilst the dark race in Southern 

 Europe, and its prototype in China, enjoys a mean temperature of 75° 

 to 80° during the moulting-season. 



Not only is the Kamtschatkan race of Sitta cmsia whiter than any 

 other climatic race of that species, but the Kamtschatkan races of 

 Pyrrhula vulgaris, Pica caudata, and Parus palustris exhibit the same 

 peculiarity. 



It has been stated (Stejneger, 'Orn. Expl. Commander Islands and 

 Kamtschatka,' pp. 230, 231) that the Kamtschatkan races of Picus 

 major and Picus minor are whiter than the Central-Siberian races of 

 those species, but this does not appear to be the case. 



In both those species, however, the Japanese races are darker than 

 the Siberian races, and more nearly resemble those of Western Europe. 

 The Japanese race of Picus major closely resembles the South-Euro- 

 pean race, whilst the Japanese race of Picus minor scarcely differs 

 from the South-Scandinavian race of that species. The Japanese 

 race of Gecinus canus is not known to differ from the European race 

 of that species, but there is good reason to believe that Siberian 

 examples are on an average greyer. 



The Japanese race of Falco tinnunculus scarcely differs in colour 

 from the race which breeds on the islands off the coast of West Africa. 

 These races are darker and more richly coloured than those in the 

 intervening country. 



Siberian examples of Certhia familiaris are whiter than those from 

 Japan or Europe, and the same remark applies to Siberian examples 



