Adults have an incomplete prenuptial molt, involving the body plumage, some wing coverts, scapulars, and tertials, in late winter and early spring, and a complete postnuptial molt in July and August. Fall birds are much more richly colored than spring adults.
Food.—The woodcock is a voracious feeder; its principal food is earthworms or angleworms, of which it has been known to eat more than its own weight in 24 hours. It is said to feed mainly at night or during the hours of twilight or dusk. The worms are obtained by probing in mud or damp earth in any place where worms are to be found, including gardens and cultivated fields. The long bill of the woodcock is well supplied with sensitive nerves, in which the sense of touch is highly developed; it can detect the movements of a worm in the soil and capture it by probing. Numerous borings are often seen close together, indicating that the bird does not always strike the worm at the first stab. Probably its keen ears also help to locate its prey. It is said to beat the soft ground with its feet or wings, which is supposed to suggest the effect of pattering rain and draw the worms toward the surface.
C. J. Maynard (1896) made the following observations on a captive bird:
The floor of its house was covered to the depth of four or five inches with dark-colored loam, in which I planted a quantity of weeds, beneath which the woodcock could hide. I would drop a number of worms on this soil, which, as the bird was too shy to feed at first, had ample time to bury themselves. At times, however, I was able to watch the bird unseen by it; then the woodcock, which had remained hidden in the corner behind the sheltering weeds, would emerge cautiously and walk over the ground, slowly and deliberately, pausing every instant or two as if listening intently. Then he would stamp with one foot, giving several sharp, quick blows, after which he would bow his head near the ground and again listen. Then suddenly he would turn either to the right or left or take a step or two forward, plunge his bill into the earth, and draw out a worm, which he would swallow, then repeat this performance until all the worms were eaten.
During dry spells, when the worms have returned to the subsoil, the woodcock must seek other foods. It then resorts to the woods, where it turns over the leaves in search of grubs, slugs, insects, and larvae. It has even been known to eat grasshoppers. Mr. Rich (1907) says that in early spring, before the alder covers are open, it feeds on ants. Frederick S. Webster (1887) reports a singular case, where the crop of a woodcock was crammed full of leaves of a common fern.
Behavior.—The woodcock is so nocturnal or crepuscular in its habits that it remains quietly hidden in its favorite covers during the day and is seldom seen to fly unless disturbed, when it flutters up through the trees with a weak, irregular, or zigzag flight, dodging the branches. When clear of obstructions, it flies more swiftly and directly, but usually for only a short distance, and soon pitches down into the cover again. One can usually follow it and flush it again and again. Toward dusk it becomes much more active, and its shadowy form is often seen flying over the tree tops and across open places to its feeding grounds. At such times its flight is steady and direct, with regular wing strokes; its chunky form with its long bill pointing downward is easily recognized. While traveling at night its flight is quite swift. When rising in flight the woodcock produces, usually but not always, a distinct whistling or twittering sound. This has led to much discussion and differences of opinion, as to whether the sound is produced by the wings or is vocal. I am inclined to the latter theory, for I have often seen a woodcock fly without whistling, and many others have referred to such a flight.
Few of us have ever seen a woodcock alight in a tree, but Mr. Rich (1907) refers to several instances where the bird has been seen to do this by reliable witnesses. Once he himself shot one in the act.
Voice.—Except during the spectacular song-flight and courtship performance, the woodcock is a very silent bird, unless we regard the twittering heard when it rises as vocal. Mr. Nichols says in his notes:
The quality of the twitter of a rising woodcock corresponds more or less to the character of its flight. When, as is frequently the case, the bird merely flutters a short distance to drop again behind the screen of undergrowth, it amounts to little more than the chirping of crickets. On one occasion when I observed an individual barely escape the attack of an Accipiter, this sound, as it rose, was less shrill and loud than often, but more rapid and sustained, with an incisive quality suggesting a rattle snake's alarm. When a woodcock rises through thick brush or brambles its wings make a whirring sound not unlike that of the bob white, accompanied by a slight twitter.