Plumages.—The downy young western sandpiper, when first hatched, is richly colored in warm, bright browns and buffs, quite different in appearance from the young semipalmated sandpiper. Behind a broad "cinnamon buff" forehead is a large, rounded crown patch extending from above the eyes to the nape, in which the down is basally black, but deeply tipped "burnt sienna"; in the center of this a cluster of buffy down tips produces a spot, which is divided by a blackish median stripe extending down to the bill; a band of pale buff, produced by down tips, encircles the sides and rear of the crown patch; there is a loral stripe and a short malar stripe of black; the sides of the head and neck are "cinnamon buff"; and a variable pattern of "burnt sienna" decorates the auricular region, behind and above the eye. The remainder of the upper parts, back, wings, rump, and thighs are a mixture of black and dark, rich browns, "bay," "burnt sienna," and "amber brown," sprinkled, in an irregular pattern, in the darker portions with tiny buff tips. The under parts vary from pale buff on the breast to buffy white on the throat and to white on the belly. The bright colors fade to dull browns and grayish as the chick grows older. The first of the juvenal plumage appears on the scapulars and then on the sides of the breast.
In fresh juvenal plumage, as seen in Alaska in June, the crown is "sepia" with "pinkish cinnamon" edgings; the nape is "drab-gray," streaked with dusky; the feathers of the mantle are brownish black, edged with "tawny" on the back and broadly edged with "tawny" and white on the scapulars; the rump, upper tail coverts, and central tail feathers are "sepia"; the other rectrices are "light mouse gray"; the wing coverts are "mouse gray," tipped with "tawny" or lighter buff; the throat and under parts are white, washed on the breast with "light cinnamon-drab," and streaked on the sides of the breast with dusky. This plumage fades somewhat during migration and the body plumage is mostly all molted before October. In their first winter plumage young birds can be distinguished from adults only by the wing coverts and a few retained scapulars and tertials. At the first prenuptial molt they become practically adult.
Adults have a complete postnuptial molt in the summer and fall, molting the body plumage in July and August and the wings and tail in November or later. The prenuptial molt in March and April involves only the body plumage. The fresh plumage, in April, is veiled with "drab-gray" tips, which soon wear away, revealing the bright nuptial colors.
Food.—Very little has been published on the food of the western sandpiper, but it probably feeds on the same things as the other small sandpipers with which it associates. Arthur H. Howell (1924) says:
Six stomachs of this bird collected in Alabama showed its food to be minute fly larvae, aquatic beetles and bugs, marine worms, and small snails.
Stuart T. Danforth (1925) found 150 bloodworms and a Hydrophilid larva in the stomach of one taken in Porto Rico.
Behavior.—S. F. Rathbun has sent me the following notes on the habits of the western sandpiper on the coast of Washington:
This is one of the small sandpipers of this region that will be found common at the time of the migration periods along the ocean beaches and on the tide flats. It occurs in flocks of varying sizes, some of which contain an exceedingly large number of birds. At times if care is used one can approach a flock quite closely, often within 15 or 20 feet, and it is of interest to watch the actions of the individuals. They are active birds, being constantly on the move as they feed, and while thus engaged keep up a continual conversation, as it were, this being of the nature of a soft, rolling whistle which is pleasant to hear. These sandpipers seem to prefer to feed at or near the waters edge, particularly where there is an ebb and flow, being very active in following up the water as it recedes and equally so in avoiding its incoming, but always at the very edge as it were. They secure their food by a skimming like movement of the bill over the surface of the mud that has just been covered by the water, and as the birds advance or retreat in following the flow it is quite amusing to observe the seeming pains taken to avoid coming into contact with it. And still at times individuals may be seen in some of the very shallow spots. It is a fine sight to see a flock of these sandpipers suddenly take alarm as they are feeding; all quickly spring into the air as if moved by the same impulse at exactly the same moment, and then form a compact body that will execute a variety of evolutions in perfect harmony. The flock will rise and fall and wheel and turn, and at times may split into several smaller ones, these to again reunite, and should one happen to stand where the light falls directly on the birds the white of their underparts as they turn is very striking. These actions may be repeated a number of times, and then without warning the flock of birds will alight and quickly scatter in search of food. Scenes like this are what give an enlightenment to the waste places and fortunately, under the protection now afforded the species, are likely to continue to be enacted in the future. But large as the numbers of the western sandpiper still appear to be, they are not comparable to those of fifteen or twenty years ago, and the cause of this decrease in their numbers is the same old story. It seems hardly possible that a bird so small could have been regarded as game and its hunting come under the name of sport, but such was the case and it brought about the logical result. One may be thankful, however, that this no longer can be done, and hope that the lapse of time may bring about somewhat of an increase in the number of these birds.
Voice.—John T. Nichols contributes the following on the calls of this species: