Cogswell 1949 Charadrius hiaticula Apr. 23 - N.W. end of Bay Farm Rd., Alameda, Alameda Co., Calif. - of some 300 or more well scattered on the higher firmer parts of the mud-flat here, a great many are in full nuptial plumage with black breast & head markings, bright orange feet and basal part of bill. These birds show antagonism toward any other plovers coming near; & several, when once excited thus, set up calling a series of: "yip - - yip - - - - yip - - - - yip - - " str., or halfway between that and: "whip - - whip - - - - whip - - - whip", occasionally this would be speeded up into a shrill trill: o o o oooooooooooooo yip yip yip yipyipyipyipyip! all of these notes are given by birds with heads lowered, facing any bird coming near. A few rushes toward the oncoming bird were noted, and once a nuptial-plumaged bird rushed a dull-plumaged (= imm.?) bird without apparent provocation. [at home: I note that Hoffman describes this behavior & describes the note as "chii" repeated & "ending with a whining"].