On first noticing me draw near they stood erect, with upstretched necks, regarding me intently and distrustfully, but their feeding operations were resumed soon after I ceased to advance. By successive runs, 8 or 10 feet in length and often executed very swiftly, they moved about quickly in various directions over soft mud or through shallow water, frequently stooping to pick up small morsels of food, but not once using their bills for probing under ground or water. _Voice._--Dr. Charles W. Townsend (1905) says that the note, which he heard several times, seemed to him "exactly like that of the semipalmated sandpiper, a rather shrill, trilling whistle." Mr. Brewster (1925) says that-- the _kreep_ call they utter in flight is sufficiently unlike that of any other wader of similar size and general coloring to be of service as a means of field identification when the birds are seen on wing. It is appreciably different from the call of any other sandpiper known to me, although not so very unlike that of the sanderling. _Field marks._--The Baird sandpiper is one of the most difficult of all this group to recognize in the field, because it has no prominent distinguishing field marks peculiar to itself. It has characters in common with any one of several small sandpipers. In color and general appearance it is most like the least sandpiper; it is decidedly larger, but size is of little value unless the two are side by side for comparison; it is lighter colored above, more extensively buffy on the breast, and has darker legs. It is a size larger than the semipalmated and western sandpipers, more buffy on the breast than either, and has a shorter bill in proportion to its size than the latter. It is about the size of the white-rumped sandpiper, but is less distinctly streaked on the crown and back; the buff breast of the Baird will distinguish it when standing or even in flight; and the white rump of _fuscicollis_ is a sure flight mark when visible. From the red-backed sandpiper, about the same size, it can be distinguished by its shorter and straighter bill and by marked color differences. It might be mistaken for a female pectoral, but the latter is more conspicuously striped above, more like a snipe in this respect, the crown is darker, more contrasted, and the breast is darker, more abruptly separated from the white belly, and more sharply streaked with dusky; when flying the pectoral shows more white in the wings. The Baird is but slightly smaller than the buff-breasted sandpiper and very much like it; but Prof. William Rowan (MSS.) has pointed out some differences. The patterns of the backs are very similar, but the buff breasted has a much paler crown and lacks the white throat and eye stripe, as well as the clear-cut white sides and black center of the rump of the Baird. The buff breasted has yellow legs and the Baird has black. The Baird shows no white in the wings in