352 BRITISH BIRDS. 
Family PICIDA, or WOODPECKERS. 
The Woodpeckers are a well-defined group of birds, and were associated 
by Forbes with the Kingfishers and Hoopoes, but are placed by Sclater in 
a suborder by themselves. Like the Kingfishers, Rollers, and Bee-eaters, 
they have two notches on each side of the posterior margin of the sternum ; 
but Huxley does not seem to regard them as nearly allied to these families 
in the modification of their cranial bones, but rather to the Swifts, the 
Goatsuckers, and the Passerine birds. They exhibit considerable variation 
in their pterylographic characters, which are said by Nitzsch to resemble 
those of the Kingfishers in some respects. In their myology and digestive 
organs they are said to be allied to the Kingfishers and the Hoopoes. 
The Woodpeckers have only one moult in the year, which takes place 
in autumn, progressing very slowly, so as not to inconvenience the bird. 
It lasts through July and August frequently into September, and in some 
species is only completed in October. 
The principal external characters of the Woodpeckers are the long wedge- 
shaped bill and the distribution of the toes, which are placed two in front 
and two behind. The wings are rounded, containing ten primaries, and 
the number of tail-feathers is either ten or twelve. They may be divided 
into three subfamilies—the Picine, or true Woodpeckers, the Picumnine, 
or soft-tailed Woodpeckers, and the Yungine, or Wrynecks, which have 
also soft tails. The true Woodpeckers may be distinguished by their 
wedge-shaped tails, the feathers of which are rigid and pointed. Like the 
Sun-birds and the Humming-birds, the Woodpeckers have a _ peculiar 
development of the tongue, which is capable of being extended to a great 
length, to assist them in catching their prey. 
There are about 330 species of Woodpeckers, which are distributed 
throughout the world, except that they are absent from Madagascar and the 
whole of the Australian Region east of Celebes and Flores. Ten species 
are found in Europe, of which four are British. 
Genus PICUS. 
The genus Picus was recognized by Linnzus in the 12th edition of his 
‘Systema Nature’ (i. p. 178), published in 1766, and, with the exception 
of the Wryneck, embraced the whole of the then-known Picide. Untfor- 
tunately Brisson did not designate any type for his genus Picus, and orui- 
