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Summary: Soft Song in Song Sparrows: Acoustic Structure and
Implications for Signal Function
Rindy C. Anderson*, William A. Searcy*, Susan Peters & Stephen Nowicki
* Department of Biology, University of Miami, Coral Gables, FL, USA
Department of Biology, Duke University, Durham, NC, USA
Introduction
Male songbirds are known for their conspicuous
broadcast songs. In most songbird species, broadcast
songs are produced at high amplitudes such that
their active space (the distance from a sound source
over which a signal is detectable) extends well
beyond territorial boundaries (Brenowitz 1982;
Wiley & Richards 1982; Dabelsteen et al. 1993; Hol-
land et al. 1998; Naguib & Wiley 2001). In addition
to broadcast songs, songs of low amplitude, variously
termed `quiet song', `twitter song', `whisper song' or
`soft song,' have been noted for some songbird spe-
cies. Examples include the European blackbird Terdus
merula (Dabelsteen 1984; Dabelsteen & Pedersen
1990), the European robin Erithacus rubecula (Lack
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