THE CALLS AND ASSOCIATED BEHAVIOR OF BREEDING WILLOW PTARMIGAN IN CANADA

We describe the physical structure, use, and possible functions of 11 calls of breeding Willow Ptarmigan (Lagopus lagopus), most of which we re given by both sexes. Both sexes had visually and acoustically consp icuous territorial calls (flight song, rattle, ''kohwa,'' and ''aroo'' (males only). ''Koks,'' ''ko-ko-ko,'' and ''krrow'' were given by bot h sexes as low intensity threat, territorial, or sexual situations, or to maintain contact with the mate or offspring. ''Purr'' and ''moan'' were given usually by females to communicate with chicks, and ''hiss' ' and ''scream'' calls by both sexes in intense defence of offspring o r mates. The sex of the caller was usually easily recognizable, as mal es had strong and rapid amplitude modulations in their calls, which fe males lacked. The most complex calls were flight songs which consisted of several calls in sequence. Unlike other nonpasserines, Willow Ptar migan do not appear to have a repertoire of calls that are graded vari ants of one another. Calls of North American populations of Willow Pta rmigan appear similar to those of European populations.