72 BRITISH BIRDS. 



From Yorkshire the disease was only noted in two places, 

 and those only in single examples, though presumably 

 there must have been others. The counties in which the 

 disease was most prevalent were : Wiltshire, Buckingham- 

 shire (S.), Berkshire (N.), Oxfordshire (S.), and Hampshire ; 

 to a lesser degree in West Sussex, West Kent, and Surrey ; 

 and it seems undeniable that the centre of the disease 

 lay in an area covered by beech wood in the Thames 

 Valley in the counties of Berkshire, Oxfordshire, and 

 Buckinghamshire, and in one place on the borders of 

 these three counties the number of diseased Pigeons 

 reached such extraordinary proportions that 2242 were 

 burnt, and it is estimated that another 2000 were 

 disposed of. From Scotland and Ireland only negative 

 reports were received. 



11. — Migratory Flocks. — Nearly all observers agreed 

 that the migratory Pigeons arrived at the end of October 

 or beginning of November, that they increased in numbers 

 during November, and decreased towards the end of 

 January, and that by the end of February most of the 

 migratory birds had gone. 



These migratory flocks probably come from Central 

 Europe, as large migratory flocks appear in Holland in 

 the autumn ; it has been often suggested that these flocks 

 come from Scandinavia, but as this bird is only found 

 in southern Scandinavia, and is not particularly numerous 

 there, this theory is untenable. 



That the disease occurred mainly in these migratory 

 flocks most observers agreed, some, indeed, asserting that 

 the resident birds were never attacked, but this is very 

 difficult to prove. 



There is little doubt that the disease was found where 

 there was a great increase of Pigeons in the autumn, 

 and, as a rule, where there were few birds no disease was 

 noted, though in one or two exceptional cases there were 

 large numbers and no disease. 



HI. — Transmission of the Disease. — Very little 

 light seems to have been thrown by schedule returns 



