[g] Mr. Willughby, Ray, and many others, imagine the principal use of the Tail to be to steer, and turn the Body in the Air, as a Rudder. But Borelli hath put it beyond all doubt, that this is the least use of it, and that it is chiefly to assist the Bird in its Ascents and Descents in the Air, and to obviate the Vacillations of the Body and Wings. For as for turning to this or that Side, it is performed by the Wings and Inclination of the Body, and but very little by the help of the Tail.
[h] See Borelli ubi supr. Prop. 182, &c.
[] It is considerable in all Water-Fowl, how exactly their Legs and Feet correspond to that way of Life. For either their Legs are long, to enable them to wade in the Waters: In which case, their Legs are bare of Feathers a good way above the Knees, the more conveniently for this Purpose. Their Toes also are all abroad; and in such as bear the Name of Mudsuckers, two of the Toes are somewhat joined, that they may not easily sink in walking upon boggy Places. And as for such as are whole-footed, or whose Toes are webbed together (excepting some few) their Legs are generally short, which is the most convenient Size for Swimming. And ’tis pretty enough to see how artificially they gather up their Toes and Feet when they withdraw their Legs, or go to take their Stroke; and as artificially again extend or open their whole Foot, when they press upon, or drive themselves forward in the Waters.
[k] Some of the Characteristicks of Rapacious Birds, are, to have hooked, strong, and sharp-pointed Beaks and Talons, fitted for Rapine, and tearing of Flesh; and strong and brawny Thighs, for striking down their Prey. Willughby Ornith. L. 2. c. 1. Raii Synops. Av. Method. p. 1.
[l] Such Birds as climb, particularly those of the Wood-pecker Kind, have for this Purpose (as Mr. Willughby observes, L. 2. c. 4.) 1. Strong and musculous Thighs. 2. Short Legs and very strong. 3. Toes standing two forwards and two backwards. Their Toes also are close joined together, that they may more strongly and firmly lay hold on the Tree they climb upon. 4. All of them——have a hard stiff Tail bending also downwards, on which they lean, and so bear up themselves in climbing.
[m] Swifts and Swallows have remarkably short Legs, especially the former, and their Toes grasp any Thing very strongly. All which is useful to them in building their Nests, and other such Occasions as necessitate them to hang frequently by their Heels. But there is far greater use of this Structure of their Legs and Feet, if the Reports be true of their hanging by the Heels in great Clusters (after the manner of Bees) in Mines and Grotto’s, and on the Rocks by the Sea, all the Winter. Of which latter, I remember the late learned Dr. Fry told this Story at the University, and confirmed it to me since, viz. That an ancient Fisherman, accounted an honest Man, being near some Rocks on the Coast of Cornwal, saw at a very low Ebb, a black List of something adhering to the Rock, which when he came to examine, he found it was a great Number of Swallows, and, if I misremember not, of Swifts also, hanging by the Feet to one Another, as Bees do; which were covered commonly by the Sea-Waters, but revived in his warm Hand, and by the Fire. All this the Fisherman himself assured the Doctor of. Of this, see more, [Chap. 3. Note (d)] of this Book.
[n] In Birds that frequent not the Waters, the Wings are in the Center of Gravity, when the Bird lies along, as in Flying; but when it stands or walks, the Erection of the Body throws the Center of Gravity upon the Thighs and Feet.
CHAP. II.
Of the Head, Stomach, and other Parts of Birds.