on the Nesting of the Avocets in the Zoological Gardens. 261



but although his bill presented at the time he was a week old


scarcely a perceptible trace of tilt, he nevertheless was seen, Mr.


Thomson tells me, though I have not observed it myself, to make


use of the lateral sweeping action to skim floating particles off the


surface of the water which is the function of the upturned bill of


the old birds. This early appearance of a habit before the


development of the structural feature upon which its proper


performance depends is worth attention, for it suggests that the


sweeping action of feeding preceded in the evolution of the


Avocet the acquisition of the upbent bill so characteristic of the


bird.


Apart from size, plumage, and colour, the most distinctive


features of the chick as compared with the adult bird are the


shortness and thickness of his legs and the shortness and straight-


ness of his bill, which falls short of the head in length. The


colouring is obviously protectively adapted to that of the littoral


arenaceous surroundings natural


to the species. The upper side


is a pale yellowish or sandy grey,


speckled and lined with black,


and the underside is white. On


the head there is a narrow median


black stripe of variable extent ac-


cordingto theindividual, and also



Fig. 2.

OORSAL VIEW OF NESTLING,

about half natural size.



Fig. 3.

SIDE VIEW OF HEAD OF NESTtWCT'

slightly enlarged.



