When the beaches skirting
river estuaries are exposed at low tide, they become the
feeding grounds of thousands of waders: dunlins, knots and
sanderlings among the various kinds. Many are winter
visitors from Arctic nesting grounds and they come to
exploit the myriads of small animals that live on and under
the surface of the beach. The diet of each kind of
waders is partly determined by the length of its beak. Some
pick prey from the surface, others probe into the mud and
sand. Some waders, such as the curlew, its smaller relative
the whimbrel, and the black-tailed and bar-tailed godwits
use their extra long beaks for probing deeply in search of
worms, crustaceans and shellfish. Often they feed by simply
jabbing at the surface as they walk forward but they also
insert the 4-5 inch beak up to the hilt and seize prey that
is inaccessible to the other birds on the shore. They use
delicate sense organs at the tip of the beak to locate their
victims by touch or sensing vibrations. The curlew and whimbrel
are distinguished by down-curved beaks while those of the
two godwits are slightly upcurved. It might be thought that
it is easier to thrust a straight beak into sand but the
advantage of a curved beak is that by rotating the tip
sweeps in an arc and searches a wider area and increases the
chances of encountering food. It is a common observation
that these waders turn their heads from side to side while
they search with their beaks deeply buried.
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