BRITAIN'S BIRDS AND THEIR NESTS. 125 



and as such is not unworthy. When it first rises from 

 its perch the wings are flapped violently, so that they 

 even touch each other with a loud flapping noise, and 

 the flight is erratic. Once clear of the trees, however, 

 the Wood-Pigeon flies with a steady and straight flight 

 of very considerable velocity. 



The other factor is disease. It has been for many 

 years recognised that Wood-Pigeons are liable to attacks 

 of a kind of diphtheria, caused by an apparently distinct 

 bacillus. The disease appears to run a course of about 

 three weeks before it proves fatal. Among its efi^ects 

 are the growth of a false membrane over the palate, 

 and inflammation and swelling in the region of the 

 gullet. The former causes the true membrane to die, 

 and the subsequent wasting away may even extend to 

 the bones. The swelling in the throat may, in the 

 final stages of the disease, be sufficiently serious to 

 prevent swallowing. Starvation probably undermines the 

 bird's powers of resistance and hastens the end, but the 

 poison itself is apparently the usual cause of death. 

 The disease occurs in epidemics, being prevalent in some 

 districts in one season, in others during a second season, 

 and perhaps almost altogether absent a third year. The 

 records so far are all for England and Wales, and the 

 general opinion is that the epidemics arise among the 

 gi'eat flocks of Wood-Pigeons that arrive in October from 

 the Continent. As many as four thousand bodies of birds 

 that perished from the disease were destroyed on one 

 estate in a single season. These great epidemics tend to 

 occur in acorn or beech - mast years ; but it has been 

 very reasonably suggested that the massing of the birds 

 owing to these supplies of food is favourable to the 

 spread of the disease, rather than that the food has any- 

 thing to do with the origin of the disease. 



