 |
|
| The Insatiable Appetite |
|
|
|
|
A beak is itself a concession to weight-saving. It's much lighter than the jaws and teeth that reptiles and mammals use to collect and process their food. Yet it's also very efficient and versatile.
Insects are almost everywhere on every tree—on twigs, in buds, crawling around in crevices of the bark—and many birds find quite enough to sustain themselves just by looking carefully. But some work harder—and greater rewards.
The nuthatch, in European wood, is indefatigable. It will eat many things, including seeds during the autumn and winter which it can crack with its work—man—like beak; but in summer insects are major part of its diet and its beak serves equally well for picking them out of the bark.
 The Greater Spotted Woodpecker is a little more specialized. It particularly likes the grubs of wood—boring beetles and the first thing to do to find them is to chisel away the bark. Its tongue extends for an inch and a half beyond its beak and has a harpoon at its tip. When that hits a grub fair and square it sticks.
Tree—boring insects are never safe when woodpeckers are around. In Galapagos, grubs of insects bore into trees here just as they do everywhere else. But no Galapagos birds have the physical adaptations with which to reach them.
Galapagos finches, however, are both intelligent and ingenious. Their beaks are perfectly adequate for stripping away bark. There's a grub under there somewhere—it can hear it. But how, without the long tongue of a woodpecker can it get it out?
It needs a tool—a spine from a cactus. It has only extracted little bits of the grub.
 Nearby, a bird from another clan of finches uses a slightly different technique. It selects a rather stouter tool that can be used not so much for stabbing as for levering. That has shifted the grub a little nearer the hole. It's not quite within reach, but it's still got that lever handy. Give it another go. And that's got the rest of it.
(CCTV-2, Man and Nature)
|
|
| Editor: ZhaoXuan CCTV.com |
|
|
|
|
|
|
