At the next molt, the first postnuptial, the adult winter plumage is assumed by a complete molt from July to December. Adults have a partial prenuptial molt, between February and May, which involves most of the body plumage, usually the tail, some of the tertials, and some of the wing coverts; they also have a complete postnuptial molt beginning with the body plumage in July or August. In the adult nuptial plumage the central pair of tail feathers are barred completely; the others are usually plain gray, but sometimes the outer pair or two are partially barred.
Food.—Very little has been published on this subject. William Palmer (1899) says:
In the ponds they feed by keeping their bills in the water and move invariably all in the same direction, heads to the wind. With care I could approach within a few feet. Much the greater part of the stomach contents of these birds consisted of hundreds of minute threadlike aquatic larvae of a midge (Chironomis). Pieces of mollusks' shell had been swallowed by several of the birds. Flies, closely related to our common house fly, and tiger beetles were detected in small quantities. Of the six godwits, five had been killed on St. Paul Island, and had fed for the most part upon midges, which were probably abundant in a fresh-water pond on the island. The sixth bird was taken on Walrus Island. It had caught over 500 specimens of a species of beetle (Aegialites debilis), the sole representative of a unique family of beetles, described some time ago and subsequently lost sight of until recently discovered again.
The above report on stomach contents was made by Dr. S. D. Judd and has been amended by Preble and McAtee (1923), who report that the items of food, ranked by bulk, are flies, 76.6 per cent; beetles, 17; mollusks, 3.6; marine worms, 1.3; and vegetable matter, 1 per cent. The jaws of marine worms (Nereidae) were mistaken for jaws of tiger beetles.
Behavior.—Doctor Nelson (1887) writes:
They frequent open grassy parts of the country and are quick to protest against an invasion of their territory. As a person approaches, one after the other of the birds arises and comes circling about, uttering a loud ku-wew with such energy as to make the ears fairly ring. If their nests are near, or they have young, they come closer and closer, some of the boldest swooping close by one's head and redoubling the din. This same note is heard upon all sides while the birds conduct their courtships, and it serves also to express their anger and alarm. At the mating season the males have a rolling whistle also like that of the ordinary field plover, but shorter. When the birds fly at this time they hold the wings decurved and stiffened and make a few rapid strokes, then glide for a short distance. On the ground it walks gracefully, its head well raised, and frequently pauses to raise its wings high over the back and then deliberately folds them. They may be decoyed when flying in flocks if their whistling note be imitated. If wounded and taken in hand, they utter a loud, harsh scream.
Mr. Brandt says in his notes:
The Pacific godwit has wonderful powers of flight, and, as it wheels about protesting against an intrusion, the slightest beat of its long, decurved wings seems, without perceptible effort, to drive it forward like an arrow from the bow. That its power of flight is extraordinary is shown by the fact that it spends the winter time of the north in southern Australia and New Zealand. It migrates along the eastern coast of Asia and is one of the interesting Old World birds that find their northeastern limit on the Alaskan shores of Bering Sea. During the love-making period, shortly after this godwit's arrival on May 15, it could be heard for an hour at a time high up in the air, as it circled about, uttering continuously its wild far-reaching cry, which was very distinctive among the medley of voices. The call of the male is often answered by the female with the syllables, tut-tut, not unlike a clucking chicken. The Pacific godwit differed from the other shore birds nesting at Hooper Bay in that individuals in immature plumage were breeding. Sometimes a gray-breasted immature female would be paired with a rich plumaged male, or again both mates would be in full color; but I encountered many pairs in which both parents showed the light grayish breast of adolescence. In fact, the immatures seemed to be in the majority. It is believed that this godwit does not assume its fully adult feathers until the beginning of the third year; but, like the bald eagle, it breeds during the second year. The earliest spring arrivals at Hooper Bay were immatures and they seemed to migrate in separate flocks. One group of about 20 richly cinnamon-breasted adults stayed in our vicinity for several days from May 20 onward. Perhaps they were resting and feeding in preparation for the final stage of their journey to more polar lands for they, as well as all the other large flocks of godwits no doubt passed on to the north. The birds that nested in the Hooper Bay region arrived in an inconspicuous manner, simply filtering into their chosen haunts and were already mated.
Field-marks.—The Pacific godwit can be easily distinguished in the field from either of our two other American godwits. The marbled godwit has much more rufous in the upper parts, particularly in the wings, and has no white on the rump. The Hudsonian is very dark on the upper parts, almost black on the wings; it has a pure white rump and a black tail. The Pacific is dull brown above, with no rufous; it has a white rump, spotted with dusky, and a tail barred with dark gray and white.