FEET OF BIRDS. 267 



or such as have their feet adapted not only for 

 perching on trees, but for walking upon the ground. 

 Some unite both these powers in the greatest per- 

 fection. The crow, the thrush, the robin, sparrow, 

 and numerous other familiar birds, are as often 

 seen in one situation as the other, and in both are 

 equally at home. But the swallow is rarely seen on 

 the ground, save when employed, by the side of a 

 wet puddle, in picking up particles of mud for its 

 nest. The flycatcher also (taking our common 

 grey species as a genuine example of the family) 

 very rarely sets its feet upon the earth, and then 

 but for a moment. The larks, on the other hand, as 

 rarely perch upon trees ; the ground is more pecu- 

 liarly their element, and the wagtails do the same. 

 Nevertheless, all these families come into the general 

 order of perching birds (Insessores), because they 

 have those external characters which so distinguish 

 them, yet modified in different degrees and pro- 

 portions. Mature, ever watchful over her creatures, 

 always makes up to them in one way what she 

 takes from them in another. Of what use or ad- 

 vantage would it be to the wagtail, that it should 

 run up trees like a woodpecker, or fly with the 

 swiftness of a swallow, when its natural food is placed 

 close to the ground? If all birds were equally 

 endowed, if all could walk, climb, run, fly, or swim 

 with the same ease and with the same perfection, 

 they must all have a similarity of structure adapted 

 for such powers ; and that variety, which is one of 

 the greatest wonders of the creation,would never have 

 existed. We therefore see gradations of the same 

 quality — those, for instance, of perching or of walk- 



