Identification marks of the stilt are excellent and it is quite an easy bird to spot in almost any circumstances. It has a rump pattern all to itself and is therefore readily detected in flight. The end of the tail is darker than that of a yellow-legs, but the white of the rump end, instead of forming a straight line across the back, is horseshoe shaped. Although the turnstone and semipalmated plovers are reminiscent, they are quite distinct and not to be confused. When wading--the birds prefer to be belly deep--the carriage of the head makes the species unmistakable. The bill is always held and thrust beneath the surface perpendicularly. This necessitates a straight neck. In profile the feeding individual can be mistaken for no other sandpiper, is quite distinct from the yellow-legs, and can really only be confused with a phalarope. The Wilson phalarope habitually wades in this part of the world, swimming only occasionally, but its markings are distinctive. A flock of stilts is the most characteristic sight and the species can be identified at a great distance. The curious position of the head just referred to and the crowding of the individuals into each other make a quite unmistakable combination. They feed practically shoulder to shoulder, seldom scattering. The yellow-legs of a flock are always scattered, and the general aspect of the individuals is entirely different. Stilts never bob their heads after the manner of yellow-legs. _Fall._--The fall migration of adults begins very early, coming along with the dowitchers and first summer yellow-legs. I have an adult female in my collection, taken on July 5, 1885, on Monomoy Island, Massachusetts. The main flight of adults comes along during the latter half of July and first half of August, in this State, and the young birds come through in August and September; but this is a rare bird here, and the flight generally lasts for only a few days. Mr. Nichols tells me that: On Long Island the stilt sandpiper is usually uncommon, occurring in small numbers often closely associated with lesser yellow-legs or dowitcher. Rarely it occurs in great waves or flights as on August 12, 1912. This flight was made up exclusively of adult birds, so far as the writer's observations went. For the remainder of that season the species was unusually common. If, in ordinary years, some 200 stilt sandpipers are present on Long Island in southward migration, there were probably 3,000 in 1912. The earliest I have seen this species south on Long Island is July 10, 1921, two or three or more individuals associated with 40 or 50 lesser yellow-legs.