208 Mr. A. R. Wallace on the Natural Arrangement of Birds. 



inquire further if any and what other groups can be naturally 

 associated with them. 



The first thing that strikes us on comparing these birds with 

 each other is, that we could hardly pick four families from the 

 whole class which should have more diversified forms of bill. 

 The resemblance and affinity between them must therefore exist 

 in other parts of their body, and we find it in their wings and 

 feet. The former are generally short, rounded, and very weak, 

 quite incapable of rapid or long-continued flight, while the latter 

 are remarkably large, powerful, and peculiarly formed. They 

 may be said therefore to be the very reverse of the Fissirostres, 

 whose grand features are large wings and small feet, while in 

 the Scansores the small wings and large feet are equally cha- 

 racteristic. But it is the peculiar structure quite as much as the 

 size of the feet to which we must pay attention. The toes are 

 always exceedingly long, and the outer toe is either turned com- 

 pletely backwards or nearly at right angles to the others. This 

 toe is often the longest of all, while the true hind toe is always 

 small, and sometimes altogether wanting. It is this peculiar 

 structure that altogether separates this group from all the short- 

 winged and strong-footed Passeres, whether they are walkers, 

 perchers, or climbers. 



The habits that result from this form of foot and wing are, as 

 might be expected, to a great extent characteristic, and will serve 

 us as a valuable guide in those cases of anomalous form and 

 structure where the position of a genus or family might be other- 

 wise doubtful. These birds then are truly arboreal, rarely de- 

 scending voluntarily to the ground. They use their wings only 

 for passing from tree to tree, and, whether frugivorous or insecti- 

 vorous, they obtain their food in or upon trees. Their motions 

 along the trunk or branches, or among the thick foliage, are 

 either true climbing, or a succession of rapid hops producing an 

 appearance of climbing. The Woodpecker runs up the vertical 

 trunk, and assisted by a peculiarly modified tail and a powerful 

 wedge-shaped bill, seeks his food beneath the bark. The Parrot 

 climbs, assisted by his hooked bill, after the fruit, which alone 

 he feeds on. The insect food of the Cuckoos is sought for upon 

 the leaves and smaller branches, and they progress among these 

 so rapidly, that they have been constantly mistaken by us for 

 squirrels or other small arboreal animals. The Toucans again 

 hop actively about the tops of lofty trees, devouring an immense 

 quantity of fruit. 



Now, though these four families have evidently more connexion 

 with each other than with any other birds, yet they present so 

 many important points of difi'erence, as to show that they are in 

 reality very distant from each other, and that an immense variety 



