82 THE WOODPECKERS 



forward and two toes backward is confined nei- 

 ther to woodpeckers nor to climbing birds. The 

 parrots, which climb after a fashion, have it; 

 but so do the cuckoos, which do not climb, some 

 of which, like our road-runner, or ground cuckoo 

 of the West, are strictly terrestrial. The " yok- 

 ing " of the toes may occur by the reversion of 

 the fourth toe, as ordinarily, or of the second 

 toe, as in the trogons ; the arrangement appears 

 to be definitely related to the distribution of the 

 tendons that control the toes. But though ac- 

 counting for the structure may give a clue to its 

 descent, it does not justify its efficiency. The 

 yoke-toed foot is not exclusively a climbing foot. 

 All our families of climbers have at least one 

 representative with but one toe behind, and this 

 clearly proves that the yoke-toed structure is by 

 no means necessary even though it may be an 

 honorable inheritance among climbers. The 

 natural conclusion is that the important point in 

 climbing is not the number nor the arrangement 

 of the toes, but the length of .at least one hind 

 toe so as to give an equally divided foot. 



There is an interesting point to notice about 

 the woodpeckers. This reversed fourth toe is 

 curiously variable in length. In the flickers, 

 with its claw, it is a little shorter than the middle 

 (third) toe with its claw ; in the red-heads and 



