424 
NORTHERN THREE-TOED WOODPECKER. 
species affects deep forests among mountains, the hilly coun- 
tries of northern Asia and Europe, and the very lofty chains of 
central Europe, whose elevation compensates for their more 
southern latitude. It is exceedingly common in Siberia, is 
abundant in Norway, Lapland, and Dalecarlia, among the 
gorges of Switzerland and the Tyrol, especially in forests of 
pines. It is not uncommon in the Canton of Berne, in the 
forests near Interlaken, though very rare in Germany, and the 
more temperate parts of Europe. It is well known to breed 
even in Switzerland, and deposits, in holes formed in pine 
trees, four or five eggs, of a brilliant whiteness ; its voice and 
habits are precisely the same as those of the spotted wood- 
peckers. Its food consists of insects and their larvae, and eggs, 
and sometimes seeds and berries. It is easily decoyed by imi- 
tating its voice. 
This species is eminently distinguished among the North 
American and European woodpeckers, by having only three 
toes, the inner hind toe being wanting, besides which it has 
other striking peculiarities, its bill being remarkably broad, 
and flattened, and its tarsi covered with feathers half their 
length : the tongue is, moreover, not cylindrical, but flat and 
serrated at the point, which conformation we have, however, 
observed in the three European spotted woodpeckers, and in 
the American Picus varius^ villosus^ puhescens^ and querulus. In 
all these species the tongue is flat, vAth the margins projecting 
each side, and serrated backwards, plain above, convex be- 
neath, and acute at the tip.* 
* Mr Swainson has thought the three-toed woodpeckers of sufficient import- 
ance to form a subgenus ; and I rather think that he will be right in his views. 
These birds were included by Koch in his genus Dendrocopus, of which they 
possess the general form and colour, but differ chiefly in the structure of the foot. 
I believe more species will be discovered in the south parts of America, and Mr 
Swainson, although he does not enter minutely into the distinctions, considers 
that there are two confounded under the northern three-toed woodpecker. The 
present bird he denominates Apternus arcticus, and retains tridactylus for the 
three-toed woodpecker of Pennant and Edwards, the Picus tridactylus of Forster. 
The chief differences are in the greater size of the former, the difference of mark- 
ing, and the relative proportion of the wings. The Northern Expedition ob- 
