A partial, first prenuptial molt, mainly in March and April, involving the body feathers, most scapulars, some wing coverts and usually the tail, produces a first nuptial plumage. Some adult nuptial plumage is acquired on the head, neck, and breast, but the head and neck are not so heavily streaked and there is less barring in lighter colors on the breast and flanks; but the mantle, back, and scapulars are very different from the adult winter or nuptial plumages; these feathers are more or less variegated, barred or spotted with ashy brown and dark sepia, and are notched, edged, or tipped with gray, grayish white or white, producing a rather evenly mottled appearance. This is apparently a nonbreeding plumage, for I have seen it only in birds taken far south of the breeding range. At the first postnuptial molt the following summer, which is complete, the adult winter plumage is assumed.
Adults have a partial prenuptial molt of the body plumage, usually the tail, scapulars, some tertials, and most wing coverts between February and May. In the nuptial plumage the crown is nearly all dark sepia; the mantle and scapulars are very dark sepia, almost black, notched or tipped with white spots; and the breast and flanks are heavily and irregularly barred with dark sepia. The white notches and tips wear away toward the end of the season. The complete postnuptial molt of the body plumage occurs in August and September, but the wings are not molted until winter. In adult winter plumage the crown is streaked with sepia and white about evenly; the breast and flanks are faintly marked, or peppered, with pale sepia; and the feathers of the back and scapulars are mainly plain "wood brown," with inconspicuous whitish edgings and notches.
Food.—The greater yellow-legs seems to prefer to feed in shallow water; its long legs enable it to wade in deeper water than most other waders, and it is often seen using them to their full extent in water up to its body. It moves about nimbly and gracefully, actively engaged in catching small minnows and water insects, delicately balanced on its long legs, bowing or nodding, as if its body were on a pivot, in a very pleasing manner. Much of its food seems to consist of small minnows, in pursuit of which it is very active and lively. Mr. Nichols has sent me the following notes on the subject:
The greater yellow-legs at times catches killifish up to as large a size as it can swallow, wading in water as deep as it can stand. Having secured a fish, it manipulates same up its long bill and into its mouth. Sometimes it catches a fish tangled in a mass of fine water weed, and in this case may either fiddle with and disengage it, or work it up to its mouth and swallow it before disengaging the bill from the weed. I have seen an unusually large fish, probably (Fundulus heteroclitus), worked up the bird's bill two or three times and turned head first to swallow, stick at the base of the bill, and drop into the water again. Finally, with a great bulging of face and throat, the fish slipped down.
Satisfied for the moment, the bird rose and flew to the leeward end of the pond hole where it had been feeding, alighted, walked up the bank, and stood in a tuft of partly dry grass at the edge of the water, quietly facing out into the breeze for some twenty minutes, although all the time alert and watchful. In this sheltered position it would not have been noticed unless known to be there.
Dr. Paul Bartsch (1899) found a greater yellow-legs in the Washington market whose throat was jammed full of top minnows. He says that many times he has "watched this bird wade out into the shallow water of the bars, moving along slowly with tilting gait, suddenly lower that long head and neck and proceed to run through the water at a speed which would have done credit to a college sprinter, quickly striking to right and left with his bill." Others have noted a similar performance.
I have occasionally seen greater yellow-legs on damp, grassy meadows where they were probably feeding on insects or their larvae, snails, worms, or crustaceans, all of which have been found in their stomachs. Lucien M. Turner refers in his notes to a bird he shot at the mouth of the Koksoak River, Ungava, on September 18, 1882, which had been feeding on the berries of Empetrum nigrum.
Three birds collected by Stuart T. Danforth (1925) had eaten exclusively animal matter: "The recognizable fragments were: Dragon-fly naiads, 65.33 per cent; aquatic Hemiptera (Belostoma species), 22 per cent; fish scales (Poecilia vivipara), 6.0 per cent; Dytiscid larvae, O.66 per cent."