Wiley, R. H.   1998.   Ranging reconsidered.   Behavioral Ecology and Sociobiology 42:   143-146.


To judge the distance to the source of a signal, solely by the structure (including overall amplitude) of the received signal, a receiver must have some information about the structure of the signal at the source.   This point is beyond dispute.

The only possible basis for such a judgment is a change in the structure of the signal between source and receiver.   The empirical questions are:   can birds do this feat,   under what conditions,   and how?


Morton (1998) criticizes the methodology of recent experiments on ranging [see Wiley and Godard 1996 and Naguib 1997], in particular playback of a single song (or brief sequences), criteria for measuring subjects' responses, and criteria for assessing subjects' familiarity with songs.   On the contrary, these new features are crucial for a clear interpretation of ranging experiments.


There is much left to be learned.   For instance, experiments have so far only assessed ranging with very coarse precision.

  • How accurately and precisely can birds range songs?
  • Is familiarity with particular songs important for accurate ranging even if not for coarse ranging?
  • Is accuracy similar for all three forms of degradation used for ranging (amplitude, frequency-dependent attenuation, and reverberation)?
  • Are there predictable differences among species or in different environments?
  • Does ranging have implications for competitive or cooperative interactions between territorial neighbors?

    Our recent experiments fail to confirm that ranging requires learning about particular song patterns.   They thus rule out for now the ranging hypothesis as an explanation for the evolution of repertoires, at least insofar as it depends on coarse degrees of ranging.   The question is open with regard to more accurate ranging.