THE "POWDER-DOWN" OF THE HERON. 289 



their stay the bill of the bird which had been applied to 

 the powder-patches so much became light blue in colour, 

 and remained so, while the other's bill was yellowish in 

 colour, streaked at times with blue. 



November 18th — a calm sunny day. A Heron perched 

 on the same fence, facing the south and with a fairly 

 warm sun shining on it. For about half-an-hour it preened 

 in a leisurely manner. At first the bill was yellow, and 

 yellow it remained. The Heron attended to the plumage 

 on the breast, the legs, the shoulders, and especially the 

 neck. It worked with the point of the bill at the bases 

 of the feathers, and then drew it among them to their 

 tips. At no time was the flat of the bill used, nor did 

 " rubbing " occur, and I did not see the bill once in the 

 areas of the powder-downs. 



I had in mind two sources of error in these observations : 

 first, in determining the colour of the bill, and, secondly, 

 in estimating the relative importance of the powder-downs 

 to the general toilet. The colours remained constant 

 when the light was reflected from the bill at various angles, 

 and at equal and different distances from two or more 

 birds. Lately I had an opportunity of examining a 

 Heron not long dead, and found that the bill was coated 

 readily with the powder, and while the blue colour was not 

 displayed prominently with the bird in the hand, it 

 became much more distinct when looked at from any 

 distance within reasonable limits. " Rubbing " may be 

 the ordinary way of treating the powder-down patches. 

 On this point more observation is necessary, but con- 

 sidering the sequence of events as I have outlined them, 

 we may suppose that the powder is carried to other parts 

 of the body by means of the bill. On the dead bird, 

 after making some of the wing feathers ragged, I found 

 it easier to mat the rami with the aid of the powder than 

 without such help, and the powder has the further merit 

 of rendering the plumage highly waterproof, which is no 

 small advantage to a wading bird, whose plumes, in the 

 absence of powder, easily become draggled with wet. 



