518 The Rev. Rgv rrr SHEPPARD on the Use 
of climbing; more especially when we consider that the Nut- 
hatch (Sitta europea) 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 *, 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 man- 
ner 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 with- 
out 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 ond for this peculiar conformation ; 
and for this purpose I take the liberty of suggesting the word comprehensorii, 
occupation 
