TOOLS AND TASKS AMONG THE BIRDS. 147 
glance now at the feeding habits of a few higher 
birds in this ght. 
Next after the owls (in our arrangement at Chap- 
ter XXX) come the parrots. Some systematists think 
them akin to owls, as shown by the white egg, reversed 
outer toe, hooked beak, ete., common to both. Now, 
if the parrot inherited these from the owls, he uses 
the toe arrangement not as a grabber so much as a 
hand to hold food in while he eats, and the hooked 
tip of the beak is not a tearing instrument, but a 
means of preventing substances from slipping out 
while being ground against the filelike surface in the 
roof of the mouth. Evidently this bony file is a de- 
velopment depending upon the hook, a case where an 
old tool in a new use provokes others. Still, this old 
tool may cause its own use, if the old conditions 
should prevail. When sheep became abundant in 
New Zealand a certain parrot left off fruit eating, and 
with its hooked beak dug holes in the animal as effec- 
tively as did ever any eagle. 
But another new use of hooked beak and paired 
toes may have kept these tools present and useful in 
the parrots, and set up the new habits of climbing 
and roosting by them. 
The case of the paired toes in the cuckoos is much 
more difficult. They are not close akin to owls, and 
it is likely that other conditions have brought this 
arrangement about. Their near relatives (and prob- 
able ancestors) are the plantain eaters—fruit eaters by 
name and habit—but our cuckoos are mostly cater- 
pillar consumers and spider eaters. That, since ac- 
