PERCHING AND WALKING. 



253 



liar mode of action on the trees. This foot has three 

 toes before and one behind, but the outer front toe is 

 more or less joined to the middle one at its base 

 sometimes at the base only, and sometimes as far, or 

 nearly as far, as the first joint. This structure of foot 

 gives the bird more firmness when perching across a 

 twig than those birds have in whose feet all the toes 

 are free ; but they have not so much action on their 

 perch, and cannot swing about so much as the birds 

 with free toes ; and they are by no means so good 

 walkers. There are, however, considerable differences 

 among them ; as, for instance, the song-thrush, which 

 finds its food on the ground, is rather a good walker, 

 while the crested wrens, which reside almost con- 

 stantly in trees, have not much less command of 

 themselves than the tits. The feet of these two 

 species will serve as illustrations. 



Song Thrush and Golden Crested Wren. 



All the migrant, and some of the resident warblers, 

 which sing from the groves and copses, and make the 

 vernal season so lively with their music, have feet of 

 this structure ; and they all sing on the perch, and 

 not on the ground or the wing. 



