ACTION OF THE WRYNECK. 355 



part of the spine and its apparatus, the legs and feet, 

 and the tail ; the former of which act as double hooks 

 in holding on, and the latter as a prop or strut ; and 

 the third, or immediately acting part, consists of the 

 head and neck, which move with great rapidity with- 

 out in the least disturbing the other parts. The wings 

 do not come into play, unless when the bird shifts its 

 position laterally, or rises from the tree ; but they 

 are, as in the case of all climbing and perching 

 birds, which have much action of the bill when 

 holding on with the feet, always held in readiness, 

 so as to come into action whenever any sudden jerk 

 may require it. 



The wTyneck, which adheres to the bark of trees 

 something in the same manner as the w^oodpecker, 

 though its action upon them is different, has the 

 sternum very much of the same structure ; only as the 

 wryneck does not hew into the wood of trees, but 

 merely searches the crevices for bark insects, it has 

 a different motion of the head, and the furcal bone 

 differently formed to suit this motion. It cannot 

 strike so forcibly with the bill, or so repeatedly in 

 one place, as the woodpecker ; but the wryneck has 

 the joints of that organ remarkably quick and free in 

 their motions, so that when it is searching the cre- 

 vices, now on the one side now on the other, the well 

 defined mesial line of rich deep brown, which marks 

 the neck and shoulders, appears to be twining up the 

 tree like a little snake. 



Zygodactylic birds, which are a very numerous 

 tribe, and the characteristic tree or forest birds of 

 the warmer parts of the world, have many differences 

 of habit, according as they depend more upon flying, 

 walking, or climbing, and according to the nature 

 of their food, and the parts of the trees, or the places 



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