This section is from the book "The Balance Of Nature And Modern Conditions Of Cultivation", by George Abbey. Also available from Amazon: The Balance Of Nature And Modern Conditions Of Cultivation.
The Great Spotted Woodpecker (Picus major), Fig. 24, lower figure, belongs to the Scansores or Climbers and the family Picidae, sub-family Picinae, distinguished by the bill being truncated at the tip, and the sides of the upper bill ridged. In this beneficent bird the bill is equal in height and breadth, and the nostrils are hidden by bristles. The tongue is exceedingly long, and capable of being protruded rapidly and to a very great length, while its sides and apex are armed with barbed horny filaments serving to impale the insect prey, and the salivary glands are largely developed, and secrete a glutinous substance, which aids the tongue in its work of capturing insects. The great spotted woodpecker is coloured black and white, with a scarlet crown. Various white spots are disposed on the black-ground, and the throat and under-parts are white. The female is red and crownless. The average length is 8 or 9 in. The nest consists of a hole in the trunk of a tree enlarged by the bill. The eggs are of white colour and number five.
These birds are continually hopping about the trunks of trees and their branches, and appear to tap on the bark for the purpose of causing insects to emerge from their concealment, the stiff feathers of their tails assisting the birds to maintain their position on the trunks of trees. But the woodpeckers scruple not to peck off the outer bark of trees infested with bark-beetle larvae, and in this way and other wholly insectivorous habits are extremely serviceable.
The Lesser Woodpecker (Picus minor) is of similar habits to the Great Spotted Woodpecker, its haunts being large woods and parks and pleasure grounds.
The Green Woodpecker (Gecinus viridis) is distinguished by the bill being keeled and curved, and its edges straight. The plumage is of a general green colour, with scarlet on the top of the head, a black beak, and yellow on the tail coverts. It is far more common than the other woodpeckers, and may often be seen in woods, woodlands, and pleasure grounds, tapping on the bark of trees and even pecking off bark to feed on bark-beetle grubs. It also devours ants and ground insects.