TOOLS AND TASKS AMONG THE BIRDS. 1538 
robin eats anything. The other thrushes confine 
themselves more to an insect diet. 
Here comes in again a striking example of how 
habit may precede structure—the task outrun the 
tool—as exemplified by the dippers or water ousels. 
They stand on the border where the wrens merge 
into the thrushes and have no external endowments 
that are not possessed by either, and yet they are as 
aquatic almost as a duck. They not only feed on the 
margin, but they dive into rapid streams, walk on 
their bottoms, and swim against their currents by a 
fluttering of the wings. It shows what a strong will 
may do in spite of special tools. The only effect thus 
far that these habits and new environments have had 
is to thicken the down beneath the feathers. When 
the bird wishes to fly it simply shakes the water out 
of its plumage and is gone much as a wren goes. 
Above the thrushes we have no American birds. 
There are some Old World caterpillar eaters, and a 
peculiar group of flycatchers, with the usual shaped 
beak and gape. These are thought to stand near the 
thrushes, and near to these last perhaps stand the 
swallows with their swiftlike shape and habits. 
We have seen enough to feel that while a bird in 
his way of getting a living may differ widely from 
his near associates, yet he may show as he eats his 
feathered social status and hint the story of his de- 
velopment in the use of his knife and his fork. 
