302 BIRD BEHAVIOUR 



but the tail is distinctly affected, and it will be 

 noticed that defective quill- and tail-growth is 

 quite common among domestic birds, as well as 

 among the above-noted Cockneyfied wild ones. 



Very perfect weather-resisting devices are to be 

 found, on the other hand, not only in the down 

 underclothing of waterfowl, but in the curious 

 cleansing and water-proofing powder to be found 

 in the plumage of so many different groups, notably 

 in Herons, Pigeons, and Cockatoos, and in the great 

 bald Carrion- Storks like the Adjutant. Although, 

 as will be seen, some of these birds are waders, none 

 are habitual swimmers, and none are such vigor- 

 ous bathers as most birds, the Cockatoos apparently 

 only bathing in showers of rain. 



Powder-dusted plumage is always very close, 

 and as it cleans itself, may be looked on as the 

 perfection of feathering, although the actual powder 

 is said to be produced by the disintegration of 

 individual feathers during growth, these " pulvi- 

 plumes " occurring either scattered, as in Cocka- 

 toos, or aggregated in patches, as in Herons. 

 Finally, it will be noticed that whenever plumage 

 is not directly concerned with promoting flight or 

 giving cover from the elements, it has a strong 

 tendency to become loose and degenerate in 

 structure, as in the Peacock's train and many Para- 

 dise-birds' plumes, as well as in the Ratite birds 

 above referred to. 



