6 BEITISH BIBDS 



which have this elaborate structure are not found at all in the 

 ostrich-like birds ; in them there is no need for a firm surface to 

 catch the air ; on the contrary, it would be, if anything, disadvantage- 

 ous to swift runners, as those birds are. The feathers, therefore, are 

 much reduced in complexity, and in some they consist only of the 

 stem and the barbs. Even in flying birds there are plenty of feathers 

 of a simple structure lying between the stronger contour feathers. 

 These are the soft feathers which are generally spoken of as ' down.' 

 Some of them are so reduced as to consist of little more than the 

 stem. The same reduction is seen in the wing feathers of the 

 Cassowary. Along the margin of the wing are a few strong black 

 spines, which are really the quills of the wing feathers with no barbs 

 at all ; they consist merely of the stem, which has not dwindled in 

 the least, but is quite as strong as it would be in a feather of use for 

 flying. In a good many birds the contour feathers and the down 

 feathers also have a kind of appendix, known as the aftershaft. This 

 is a sort of supplementary feather arising from the stem just at the 

 point where the barbs, begin, and having precisely the structure of a 

 small feather. In the Emu and the Cassowary this aftershaft is fully 

 as large as the main feather ; from each stem in these birds arise as 

 it were two feathers. 



The most curious modification, however, of the feather is into 

 that structure known as a * powder-down.' These feathers have, as 

 their name denotes, a powdery appearance, which is due to the 

 continual breaking off of the fine ends of the barbs ; the feathers 

 themselves are soft, and belong to the variety of feathers which 

 have been described as down feathers. The dusty matter which 

 they give off has been described as ' dry and yet fatty to the touch.' 

 They are found in various birds ; they do not characterise any one 

 particular group, except the Heron tribe ; some Parrots have them, 

 a few Hawks, and certain other genera. It has been said that they 

 are phosphorescent ; and it has been suggested that their presence 

 in the heron is of use to it in its fishing. The light, it is thought, 

 attracts the small fishes within reach of the heron's long bill. But 

 this appears to be one of those exaggerations founded upon actual 

 fact which are so common hi natural history. 



Another important fact about a feather is its colour. There is 

 no purely white bird hi this country and not very many that are 

 chiefly white. But there are some, like the Gulls and the Storks. 

 The nearest approach to an absolutely white bird is the beautiful 

 little Egret, whose plumes are, unfortunately, so much used in 



