244 BRITISH BIRDS. 



pigeons are to be found tog-ether in our Engiish woods, 

 and also seems to correspond with those years in which 

 there is a plentiful supply of acorns, beech-mast, etc. 

 Apart from the laboratory evidence that the disease can 

 be inoculated from one pigeon to another, it cannot be 

 doubted that transmission occurs in nature, for the in- 

 cidence of the disease in a flock resembles that of a 

 contagious disease in any overcrowded commiuiity. 

 Exactl}^ hoiv the disease is spread is unknown, but it is 

 possible that acorns, which have been eaten by infected 

 pigeons, are regurgitated and eaten by other pigeons. 



Much is to be learnt as regards this disease : how it 

 comes, why it comes, and when it comes : and much data 

 is required to fill up the missing links in the etiology of 

 the disease. 



To those readers of British Birds who have oppor- 

 tunities of studying this disease I would suggest the 

 following lines of investigation : — 



1. Distribution of the disease in the British Islands. 



2. The times of year at which the disease is noted. 



3. The percentage of individuals in a flock affected. 



4. Relation of the disease to the food supply. 



5. Observations on the course and length of the 



disease. 



6. Evidence of transmission of the disease. 



7. Whether the disease occurs in young or old, or 



both. 

 At the same time, when investigating this disease, I 

 would suggest two other matters which might be looked 

 into. The first is the apparent sj)oradic migrations of 

 Wood-Pigeons during the winter (this probably is depen- 

 dent on food supply, but more evidence is wanted) ; the 

 second is a disease of the wing-feathers which Wood- 

 Pigeons are especially liable to. The disease seems to 

 attack the growing feather, which then dries up and ceases 

 to grow, and in many instances the bird is incajDable of 

 flight. This disease occurs every year, but little is known 

 about it, and observations on the same lines as I have 



