Adults have a complete molt from July to October and an incomplete molt from February to June, similar to that of the young bird, producing the distinct and well-known winter and nuptial plumages.
Food.—The northern phalarope obtains most of its food in the water, on the ocean or in bays or in brackish pools or in fresh-water ponds. Its characteristic and best-known method of feeding, on which many observers have commented, is to swim rapidly about in a small circle or to spin around in one spot, by alternate strokes of its lobed feet; this quick whirling action is supposed to stir up the minute forms of animal life on which it feeds and bring them within reach of its needlelike bill, which it jabs into the water two or three times during each revolution; the spinning motion is often very rapid and sometimes quite prolonged, a curious performance to watch. We saw this many times in the Aleutian Islands where small flocks were constantly seen spinning around about the old piers or feeding in the surf off the beaches where they floated buoyantly over the little waves or fluttered over the crests of the small breakers.
William Brewster (1925) describes an interesting feeding performance, at Umbagog Lake, Maine, as follows:
Alighting again, about 100 yards off, it began fluttering about in circles, now narrowly clearing the water for a yard or two, next hitting against or skittering over the surface, acting indeed, for all the world like some enfeebled butterfly or clumsy moth, alternately attracted and repelled by a forest pool lying in deep shadow. This singular performance was occasionally varied by more pronounced upward flights, extending to a height of several feet, and apparently undertaken in pursuit of flying insects, passing overhead.
Both the northern and the red phalaropes feed in large numbers at sea, often being associated together; their favorite feeding places are in the tide rips, on or around floating masses of seaweed, in the vicinity of whales or near schools of fish. George H. Mackay (1894) writes:
On May 25, 1894, about 10,000 (as carefully estimated) were observed resting on the water around the "pigs" (rocks lying off Swampscott), occupying an area of about a mile radius. They were feeding on the red whale bait (brit) some of which was taken from them. I am informed that these birds follow the mackerel, which also feed on this brit, by their pursuit of which it is driven to the surface, and is then obtainable by the birds. I am also told that in the Bay of Fundy the phalaropes so frighten the mackerel when they come to the surface in pursuit of the brit, that the fish sink themselves. To prevent this, the fishermen carry at times quantities of liver cut up, which they throw out to attract these birds and keep them away from the fish in order that they may be better able to capture the latter.
Dr. Alexander Wetmore (1925), in his report on the food of the northern phalarope, gives the results of the examination of 155 stomachs, collected in Alaska and in the United States, from May to October, inclusive; flies and the larvae of mosquitoes were the largest element, 32.8 per cent; the true bugs (Hemiptera) came next, 31.8 per cent, including water boatmen and back swimmers; beetles represented 16.5 and crustaceans 9.3 per cent; the remainder contained dragonfly nymphs, spiders, marine worms, small mollusks, a few small fishes and a few seeds. Various other insects and their larvae, many of which are injurious, are included in the food of this bird.
Behavior.—In flight these phalaropes remind one of the smaller sandpipers; their flight is swift and often erratic; when flying in flocks they twist and turn and wheel back and forth like a flock of peeps, flashing white or dark gray, as breasts or backs are turned toward the observer. Mr. Brewster (1883) has seen them pitch "down from a considerable height with closed wings, much as snipe will do under similar circumstances." Again he (1925) speaks of seeing one "rise abruptly to a height of 15 or 20 feet, and poise there for a moment, beating its wings and shaking its tail in a violent and peculiar manner."
It is while swimming on smooth water that the northern phalarope seems most at home, most graceful, charming, and confiding; it is usually very tame and easily approached, but sometimes, especially when in large flocks, it seems to be afraid of a boat and keeps beyond gun range. It swims lightly as a cork, its thick coat of breast feathers giving it great buoyancy, its head is held high and carried with a graceful nodding motion. When a flock alights on the water, the individuals soon scatter and swim about rapidly and independently in zigzag lines or circles, jabbing their bills into the water in a nervous and excited manner. I have never seen them dive and doubt if they can do so, as they seem to have great difficulty in getting under water, even to bathe. They frequently alight on floating masses of seaweed, where they run about and feed with all the nervous activity of small sandpipers on a mud flat. Roland C. Ross (1924) made some interesting observations in southern California; he writes:
"The northern phalarope is quite fearless in this region, but seldom does one find the birds so confiding as in the following instance: Mr. Ray Francisco, the warden for the gun club on this marsh, was working in water a foot or two deep, pulling out sedges, dock, and arrow-weed. The northern phalaropes took an interest in this roiled up water and drew close to dab at the surface and "whirligig" about in their unique way. As the man kept at work they drew nearer until actually about his feet. They stayed with him until he stopped work in that section. They were observed sleeping on land and water, bill along the back under a wing. Their ablutions were absurd attempts to get a swanlike breast and neck under water, when such airy grace and buoyancy forbade any subaquatic ventures. To get the proper ducking the phalarope stretches up and drives his pretty head and breast down in the water, which effort promptly forces his tail end up; whereupon like a cork he rebounds, to ride high and dry above the water with hardly a sign of moisture on the close-fitting plumage. At once he jerks up and ducks again, and again, all to little avail, seemingly. This up-jerk and ducking motion can be observed at a good distance, and the birds may be identified by it."