12 Presidential Address : 



are at other times so pronounced as to constitute a very- 

 serious defect in the feather. Where at all conspicuous, 

 their presence results in a great depreciation in the value of 

 the plume. Indeed, it has been estimated that in South 

 Africa the annual losses to the farmer from the production 

 of these defects amounts to as much as £25,000. 



When the investigations were first undertaken, numerous 

 explanations were prevalent as to the cause of the bars. 

 Almost every Ostrich farmer had his special theory, but 

 scarcely any two were found to agree. A few preliminary 

 experiments were sufficient to .%how the fallacy of many of 

 the current theories, and no one now believes that the para- 

 sites of the bird are the direct cause of the defects, nor yet the 

 practice of quilling, the preening of the feathers, not even in- 

 breeding. It has been shown that similar barring defects 

 may occur in the feathers of all birds, and this fact alone 

 would lead one to suspect the cause to be a very general one, 

 something inherent in the actual formation of all feathers, 

 not a process peculiar to the Ostrich. 



The bar is formed at an early stage in the growth of the 

 feather, even while the part of the feather is still within the 

 socket. Sometimes it can be seen that a bar corresponds 

 with each day's feather growth, and this fact also throws 

 considerable light upon the problem. But what the farmer 

 wishes to know is under what conditions the defects w^ill, or 

 will not, be produced ; and it is towards the determining of 

 these practical conditions that the experiments are being 

 directed. In one notable experiment it was shown that 

 exposure of a bird to two days' inclement weather, while its 

 feathers were at an early stage of their formation, sufficed to 

 produce a very conspicuous bar on every growing feather. 

 Such instances are, however, probably rare, and many 

 other causes are at work. It is almost invariably found that 

 a bird in a weak condition of health will have its plumes 

 grown during the period freely barred, and similar results 

 often follow when a bird is subjected to a change of con- 

 ditions. Anything, in fact, wdiich interferes with the regular 

 normal activity of the animal may reveal itself by feather 



