236 The Bird 
bird at first feeds upon regurgitated food, taking it drop 
by drop from the bill of the old bird, it of course has 
no need of the curved beak of its parents. Later, when 
its bill has increased in length and has begun to be marked 
by the ultimately sharp angle, the birds begin to sift 
from the coral mud the small mollusks of which their 
food consists. 
Until its wings are full-feathered the young skimmer 
is compelled to limit its wanderings to the sand-dunes 
along the shore near its nest. Thus, although at birth 
the lower mandible is a trifle longer than the upper, yet 
even when the birds are half-grown the disparity in length 
between the two mandibles is but slight. Later, when 
the young bird is able to join its parents in their skimming 
of the seas, the lower mandible quickly attains its full 
development. The friction of the water upon the bill 
must be considerable, as in a skimmer which I have had 
for years in captivity, the lower mandible grew remark- 
ably fast, measuring 6? inches from base to tip when 
the bird was eighteen months old. 
Herons and ibises, through all the years, sought their 
food in much the same places as have ducks; the straight- 
billed herons seizing their living prey with a single light- 
ning dart, as it swims past them; the spoonbills spatter- 
ing in the shallows; and the curved-beaked ibises prob- 
ing every crevice along shore. The spoonbills swing 
their necks and heads from side to side, as they walk 
slowly through the water, gleaning their food with the 
motion of a mower wielding his scythe. Two of the 
herons are interesting enough to hold our attention for 
