(_Dendrocopus major_)
It is not a little remarkable that such nearly allied birds as the
great green woodpecker, or yaffle, and the two kinds of pied or
spotted woodpeckers should present such remarkable diversity in the
matter of colouring; the former being mainly olive-yellow with a
red skull-cap in both sexes, while the other two are pied above and
chiefly white below, with a red band at the back of the head of the
cock alone. A third group is represented by the great black woodpecker,
which is wholly sable, with an ivory-white beak. The difference in
the matter of colouring between the green and the pied species is
probably due to their different habits, the former being to a great
extent a ground-bird, fond of frequenting lawns and meadows near
woods for the purpose of digging up ants’ nests, while the other two
are almost completely arboreal. In the dappled shade cast by the
leaves--especially those of pines--on the trunks of trees, these pied
birds are comparatively inconspicuous; while among grass of moderate
length the green woodpecker is absolutely invisible. It is further
noteworthy that the pied species have most of the under surface of the
body white, whereas in the green woodpecker the same aspect is grey.
To a bird walking on grass a white under surface would certainly be
no protection; but in bright sunshine on the trunk of a tree such a
surface would undoubtedly tend to render the bird inconspicuous, as it
would counteract the effect of the dark shade thrown by the body, in
precisely the same manner as in the case of white-bellied quadrupeds.
Very curious is the fact that while, as already mentioned, the red band
on the back of the pied species occurs in the adult only in the males,
such a band is found in both sexes of the immature birds. This fact,
coupled with the occurrence of a red head in both sexes of the green
species, may be taken as an indication that red on the head was at one
time a feature in all woodpeckers, but that for some reason it has been
discarded in the females of the pied group.
[Illustration]
Woodpeckers present some of the finest examples of the adaptation
of bodily structure to be met with in the whole animal kingdom. The
strong, conical beak is, for example, admirably suited for chiselling
out, by repeated blows of the head, rotten wood in insect-infected
trees, or prising off loose pieces of bark in order that the bird may
be able to get at the insects and other creatures lurking beneath.
Then, again, the short legs and the curious structure of the feet, with
two toes turned forwards and the other backwards, enable these birds
to obtain the most effective foothold on smooth, slippery bark.
Lest, however, the feet should prove ineffectual, the bird is aided
in climbing by its tail, the feathers of which have unusually strong
quills, the tips of these being bare and shiny. When this tail is
pressed firmly against the bark, the stiff tips of the feathers afford
very considerable support to the ascending bird.
The climax in the way of special adaptation is presented, however, by
the woodpecker’s tongue, which, owing to the form and structure of
the supporting bones, can be thrust out a long distance in advance of
the tip of the beak, and is covered with a sticky secretion to which
insects adhere. A similar structure obtains in the tongue of the
wryneck; but there are certain foreign woodpeckers in which that organ
is normal.
By means of its strong beak, the spotted woodpecker chisels out in
the trunk of a tree, where the wood is more or less decayed, both
a sleeping and a nesting hole. A circular entrance leads for some
distance horizontally into the heart of the stem, after which the
hole descends vertically for some way, and then expands into a large
dome-shaped chamber, which serves as a receptacle for the clutch of
three to eight white eggs, these being incubated by the male and female
birds alternately. It is very generally believed that woodpeckers
live entirely upon insects and other invertebrate animals; this,
however, is a mistaken idea, for they likewise eat various kinds of
seeds and berries, as well as nuts and walnuts, which they crack in
nuthatch-fashion. The cry of the pied woodpecker is either a short and
sharp “hi, hi,” or a harsh and resounding “hæ, hæ”; but a more familiar
sound is the tapping on the bark of the stem or larger boughs by the
beak, in order that the bird may ascertain whether the wood beneath
is sound or rotten. Very characteristic is the undulating flight of a
woodpecker, the bird generally dropping suddenly near the end of its
course, so as to alight only a short distance from the root of the
selected tree, up the stem of which it then rapidly climbs.
The larger spotted woodpecker frequents woods with different kinds of
trees; but its special favourites are pines, poplars, and willows.