of climbing; more especially when we consider that the Nuthatch (Sitta europæa) and Tree-creeper (Certhia familiaris) have their toes placed in the usual manner, and yet run up and down trees with as much facility as the Woodpeckers. The use of the pedes scansorii[1], then, to the Cuckow (as they evidently, in this case, conduce not to climbing,) I judge to be this: It is well known that this bird will oftentimes sit by the half-hour together on the bough of a tree vociferating its loud and pleasing note; in doing this it sits remarkably forward, and appears in constant agitation, continually moving its body up and down with great elegance: now, as it sits so forward whilst using this exertion, it would be liable to lose its balance and quit its hold, had it only one toe behind; whereas, by the contrivance of two, it is enabled strongly to adhere to the branch.
Psittacus also has the pedes scansorii, and is actually a climbing genus; yet does not this conformation in my opinion in any manner conduce thereto. To say that Parrots assist themselves with their beaks in climbing, would not argue the pedes scansorii to be of no utility. Their real use to this genus seems to be not only to grasp their food (for the foot of the Parrot serves the purpose of a hand in that respect), but to enable them to step securely from one branch to another, and likewise to hang suspended, as they often do; in which case the two toes before and two behind certainly give stability to their hold.
With respect to the Pici, rather a clumsy tribe, the very stiff feathers in the tail are of material service to prop them up in the act of climbing: not so the pedes scansorii, for the Nuthatch without them runs up trees equally well. Of what use then can these be to the Woodpecker? I answer, that in boring trees, (in which
- ↑ I think a more appropriate term might be adopted for this peculiar conformation; and for this purpose I take the liberty of suggesting the word comprehensorii.
