At the following molt, the first postnuptial, the adult winter plumage is acquired, characterized by the bluish-gray mantle and the white under parts. This molt is complete; it begins in July and is sometimes completed in August, but more often it is prolonged into September or later. Adults have a partial molt in the spring, from March to May, involving the contour feathers, the tail, some of the tertials, and some of the wing coverts; the remiges are not molted, and some of the old scapulars are retained. The adult postnuptial molt, from July to December, is complete.
Food.—During the month or so that they are on their northern breeding grounds the red phalaropes are shore birds, feeding in the tundra pools or along the shores, but during the rest of the year they are essentially sea birds, feeding on or about the floating masses of kelp or seaweeds, or following the whales or schools of large fish; hence they are aptly called "sea geese," "whale birds," or "bowhead birds." They occasionally come in to brackish pools near the shore or rarely are seen on the sandy beaches or mud flats feeding with other shore birds. Outlying rocky islands are often favorite feeding places. Ludwig Kumlien (1879) writes:
Whalemen always watch these birds while they are wheeling around high in the air in graceful and rapid circles, for they know that as soon as they sight a whale blowing they start for him, and from their elevated position they can, of course, discern one at a much greater distance than the men in the boat I doubt if it be altogether the marine animals brought to the surface by the whale that they are after, for if the whale remains above the surface any length of time they always settle on his back and hunt parasites. One specimen was brought me by an Eskimo that he had killed on the back of an Orca gladiator; the esophagus was fairly crammed with Laernodipodian crustaceans, still alive, although the bird had been killed some hours; they looked to me like Caprella phasma and Cyamus ceti. According to the Eskimo who killed it, the birds were picking something from the whale's back, I have often seen them dart down among a school of Delphinapterous leucas and follow them as far as I could see. On one occasion a pair suddenly alighted astern of my boat and were not 3 feet from me at times; they followed directly in the wake of the boat, and seemed so intent on picking up food that they paid no attention whatever to us. They had probably mistaken the boat for a whale.
In northeastern Greenland, Manniche (1910) saw them hunt flying insects on land; he also says:
Some 20 analyses of stomachs proved that the phalaropes in the breeding season chiefly feed on small insects, principally gnats and larvae of these. The esophagus and stomachs of several birds killed were filled with larvae of gnats, which in vast multitudes live in the fresh-water ponds. In a few stomachs I also found fine indeterminable remnants of plants (Algae?).
W. Leon Dawson (1923) describes their feeding habits at the Farallones, as follows:
Three red phalaropes, all female I take it, although none of them in highest plumage, and one northern, also a female, just under "high," are pasturing at my feet in a brackish pool some 20 feet long, 10 feet wide, and 2 feet deep. The waters of the pool teem with a minute reddish crustacean (?) shaped like an ant, less than a thirty-second of an inch in length and incredibly nimble. The insects progress by leaps, and are visible only at the moment of arrival. Yet these birds gobble them up one at a time with unerring accuracy and with a rapidity which is nothing short of marvelous. The reds work habitually at the rate of five dabs per second, i. e., 300 a minute, while the northern, with a longer beak and a much daintier motion, works only half as fast.
The following observation was made on a California beach by Roland C. Ross (1922):
Kelp flies seemed to satisfy its sporting instincts and hunger, and the bird stalked them slowly and pointedly one by one. With bill and neck outstretched and lowered in line with a fly on the sand, a slow advance was made until with a pounce the hunt closed. If the fly escaped, the phalarope sometimes ran after it, bill out. Another pose interested me. On finding a kelp mass decaying and drawing flies, the phalarope approached closely and so low that his breast touched the ground, but the rear of the bird was high up. At times he would remain with breast down and pick at the flies much as a dusting fowl picks up a stray grain. Mr. L. E. Wyman reported similar "breast to ground" actions of two phalaropes he saw feeding by a kelp mass on the beach.