Song Variation in a Population of Brown Towhees

Abstract

' With the advent of new methods of analysis, the study of variation in bird song can be approached with more objectivity than has hitherto been possible. As with morphological characters, careful study of variation may throw some light on the kind of selective influences to which vocal signals and other communicatory behavior are subject. The problem of describing variation in behavior is confounded by the extensive variation which we sometimes find within the same population and even within the same individual at different times. In a previous paper (Marler and Isaac, 1960) we have given a preliminary description of the situation in a simple case, the song of the Chipping Sparrow (Sp&eUa pas-se~inu), in which variation within the individual is minimal. The singing of the Brown Towhee (Pipilo jtiscus) is somewhat more complex and it is our intention in this paper to establish the limits of variation in the songs of the individual and in a sample of a number of individuals from the same geographical area. ACKNOWLEDGMENTS