is the fact that in their case the
true hind toe is lacking, while the outer front toe is bent backward,
or "reversed," as it is called, and is thus made to do service for a
hind toe. The other species of woodpeckers have four toes, two in
front and two behind, the outer one of the latter pair being a reversed
digit. Why some of the woodpeckers should have four toes and others
only three is an unsolved enigma, and is especially puzzling in view of
the fact that the four-toed kinds do not seem to possess any advantage
over their cousins. The tridactyl species are as expert climbers as
any members of the family, and are extremely hardy birds, too, some of
them dwelling the year round in cold northern climates, where the food
question must often be a serious one.

[Illustration: Spotted Sandpiper, or "Peet-weet"]

Here is still another conundrum for the bird student: Why do the
four-toed woodpeckers have two hind digits, despite the fact that they
always clamber upward when they take their promenades on the boles and
branches of the trees, whereas the agile little nuthatch, which glides
upward or downward, as the impulse moves him, has only one rear toe and
three in front, like the true perchers? Nor is it less puzzling that
the cuckoos, which are perching birds, should have two toes in front
and two behind. Then, there is the little brown creeper which never
perches and is forever creeping, creeping, upward, upward--save, of
course, when it takes to wing--and yet its toes are arranged in the
normal percher style, the hind digit having an especially long, curved
claw. It is a mistake to suppose that all the problems of the bird
world have been solved.

Look at the different kinds of birds' feet and see how wisely they have
been planned for the various purposes to which they have been applied.
In order that a bird may use his feet with the greatest dexterity in
perching and flitting, his digits should be as free and movable as
possible; and so we find that the toes of the perchers are usually
cleft to the base, are long and slender, easily opened and closed, and
possess the power to grasp an object firmly. The same is true of the
raptorial birds, or birds of prey, which are strong perchers and depend
largely for their food supply on clutching their victims while on the
wing. In all these birds the hind toe is also well developed, and is
on the same plane as the anterior digits--a wise adaptation of means to
ends