WOODPECKERS 165 



tail and feet form, in fact, a tripod, on which the bird sits safely even 

 upon a vertical tree- trunk, and it can actually sleep in this position. 

 The support afforded by the roof-like tail is due to the following characters : 



(1) The quills of the tail-feathers are very strong and hard. 



(2) The tail-feathers of each side lie one above the other, and not by 

 the side of each other, hence they mutually support each other (acting, 

 in fact, like a single pair of very strong feathers). 



(3) The vanes of the tail-feathers are of equal breadth on both sides, 

 narrowing at the tip, and their barbs are very stiff and inclined downwards. 



The woodpecker ascends trees by hopping (simultaneously with both 

 feet) up the trunks in short leaps or in spiral lines, at the same time 

 moving its wings forwards by jerks. (In jumping over a ditch we thrust 

 our arms forwards. Why cannot the woodpecker move along the trunk 

 from above downwards ?) During its ascent the bird incessantly taps the 

 tree with its beak, immediately after each tap running over to the oppo- 

 site side of the trunk. By this tapping it alarms the insects, who abandon 

 one side of the tree to escape their enemy, and run straight "into 

 his arms" on the 'other side. The tapping of the woodpecker's beak 

 makes a noise which can be heard from a great distance in the woods. 



4. By means of powerful blows with its long, straight, wedge-shaped 

 beak, which is covered with a solid layer of horn, the woodpecker gets at 

 the insects underneath the bark or within the wood. The upper mandible 

 is especially powerful, being further strengthened by three longitudinal 

 ridges of horn. It projects slightly beyond the under bill, and does not 

 terminate in a point, but in a vertical, chisel-shaped, cutting edge. By 

 means of this excellent implement the bird not only peels off the bark, 

 but chips off the hard wood in splinters, whence it has not without 

 reason been called " the carpenter of the woods." In connection with 

 these peculiarities we must consider the following additional facts : 



(a) The neck being short enables the bird to deal well-directed blows. 

 (If we wish to deal a safe blow, we grasp the hatchet near the head.) 



(b) In taking aim for a blow, the woodpecker presses its tail against 

 the trunk of the tree, the fore-part of its body being bent backwards. 

 This has the effect of bending still more the quills of the tail-feathers, 

 which (during rest) are to some extent curved upwards. With the 

 cessation of the pressure, the feathers rebound like springs into their 

 original position. They thus force the hinder end of the body away 

 from the tree-trunk, and the fore-part towards it, so increasing the force 

 of the stroke. 



(c) The head, being relatively large and heavy, also aids in augmenting 

 the effects of the blows inflicted by the beak. (To deal a heavy blow, we 

 use a heavy hammer.) 



