WHAT IS A BIRD ? 19 



A very remarkable form of down-feathers is 

 found in many birds, such as the common heron^ 

 the bittern, some hawks, parrots and tinamous. 

 This is known as " Powder-down." The exact 

 nature of this powder-down is not yet thoroughly 

 understood. It is peculiar, in that it is constantly 

 crumbling away into an exceedingly fine dust, 

 which feels something like Fuller's Earth when 

 rubbed between the fingers. In the herons, it 

 grows from enormous patches on the body — a 

 pair on the breast, and a pair over the thighs. 

 These, when the bird is skinned, appear on the 

 inner surface of the skin as large dark- coloured 

 areas. 



Filo-plumes would hardly be recognised as 

 feathers at first sight. Exactly what is meant by 

 a filo-plume can be seen at a glance by a visit to 

 the kitchen, or the nearest poulterer's when a 

 newly plucked fowl is undergoing preparation for 

 its appearance later on in the dining-room. You 

 will notice that, now that the feathers have been 

 removed, the body appears to be sparsely covered 

 with long delicate hairs. These are the filo- 

 plumes. Their true feathery nature can only be 

 fully made out by an examination under the 

 microscope, before they have quite completed 

 their growth. 



Sometimes the filo-plumes attain great length, 

 and are then quite conspicuous. In the cor- 

 morant, for instance, they form a large white 

 patch on each side of the body during the 

 nesting season of the year. 



Another, and very greatly modified kind of 

 feather occurs in the form of eyelashes, and what 



