The feathers of birds appear to be nourished and preserved in a remarkable manner; especially those that much frequent waters, for they have a larger supply of oily substance, with which to trim them. Lest the feathers should be injured by exposure to the air, every bird is furnished with a gland situated on the rump, containing a proper quantity of oil, which it presses out with its beak, and with which it occasionally anoints them. In water fowls, this oil is so plentiful, that it even imparts a degree of rancidity to the flesh; and by it, their plumy coat is rendered completely waterproof.
As God made the fowls “that they might fly in the firmament of heaven,” so has he adapted the form of their bodies, and the structure and disposition of their plumage, for that very purpose. The head and neck in flying, are drawn principally within the breastbone, so that the whole underpart exhibits the appearance of a ship’s hull. The wings are used as sails, or rather oars, and the tail as a helm or rudder. By means of these, the creature is not only able to preserve the centre of gravity, but also to accelerate its speed through the air, either straight forward, circularly in any kind of angle, as well as upward or downward. Though the greatest part of the aërial creation are adorned with feathers, yet has the Deity enabled several to fly without them; such as the Bat, one species of Lizard, two sorts of fishes, and numberless kinds of insects.
The skill with which birds erect their houses, and adjust their apartments, is inimitable. The caution with which they conceal them from the searching eye, or intruding hand, is admirable. They fix their nests on the pliant branches that wave aloft in the air, or are suspended over the flowing stream: by these means the vernal gales rock their cradle, and the murmuring waters lull their young; while both concur to terrify their enemies, and have a tendency to prohibit their approach. Some hide their downy offspring from view, amidst the shelter of entangled furze. Others, with wary solicitude, place them in the centre of a thorny thicket. And thus, by a variety of expedients, they are generally as secure, as if intrenched behind an impregnable mound.
“Some to the holly-hedge
Nestling repair, and to the thicket some;
Some to the rude protection of the thorn
Commit their feeble offspring: the cleft tree
Offers its kind concealment to a few,
Their food its insects, and its moss their nests.
Others apart, far in the grassy dale,