A50 REPTILES AND BIRDS. 
ascension by extending their toes, supplied with bent claws, upon the 
trunk of a tree, and maintain themselves hanging there ; then move 
themselves a little farther by a sudden and jerked skip, and so on. 
These movements are facilitated by the disposition of the tail, formed 
Fig. 176.—Ivory-billed Woodpeckers. 
of straight resistant feathers, slightly worn away at their extremities, 
which, pressed against a tree, serve as a support to the bird. Thanks 
to this organisation, Woodpeckers traverse trees in every direction—- 
downwards, upwards, or horizontally. . Woodpeckers are of a timid 
and restless disposition; they live alone in the midst or on the 
