sequence in which multiple song types are sung. That is, different males may
share song types but sing them in individually distinctive temporal patterns.
The role of this final cue has not been extensively studied in songbirds, but
there is some evidence to suggest that European starlings are sensitive to
the sequence of motifs within familiar song bouts (Gentner and Hulse
1998).
For species in which males sing multiple songs, the four mechanisms
outlined above may not be mutually exclusive. There is no a priori reason
to believe that vocal recognition in a single species relies on individual
variation coded in only a single dimension, nor is there any reason to
suspect that all species of songbirds use the same recognition strategies.
Given the approximately 4,500 different species of songbirds—each singing
acoustically distinct songs and the occurrence of vocal recognition in a wide
range of behavioral contexts, it is likely that vocal-recognition information
is coded at multiple levels throughout a songbird’s repertoire (Braaten
2000).
3.3.3. Laboratory Studies
Given the likely diversity of vocal-recognition behaviors across songbird
species, it is reasonable to consider whether there are corresponding peripheral perceptual specializations among songbirds that in theory might
provide an “open channel” of communication within a species while limiting confusion across species. For instance, different species might concentrate the spectral energy with their songs in defined spectral bands. This
hypothesis is supported by several observations of species-specific advantages during operant discriminations of multiple conspecific and heterospecific songs in several different species (Sinnott 1980; Okanoya and
Dooling 1990; Cynx and Nottebohm 1992; Dooling et al. 1992). However,
the overwhelming data from psychophysical studies of hearing in birds indicate that most basic sensory processing capabilities (e.g., frequency sensitivity) are conserved across songbird species (Dooling et al. 2000). Thus, it
appears that biases for the discrimination of species-specific vocalizations,
and hence mechanisms for vocal recognition, result from evolutionary or
ontogenic changes in central processing structures. This inference is consistent with the more general assumption that the cognitive processes underlying vocal recognition take the neural representation of acoustically
complex signals (i.e., song) as their input. Recent laboratory studies of
European starlings have addressed these questions by determining more
precisely the form of the acoustic signal controlling recognition in this
species.
Male starlings tend to present their songs in long episodes of continuous
singing referred to as bouts. Song bouts, in turn, are composed of much
smaller acoustic units referred to as motifs (Adret-Hausberger and Jenkins
1988; Eens et al. 1991), which in turn are composed of still smaller units
358
T.Q. Gentner and D. Margoliash
share song types but sing them in individually distinctive temporal patterns.
The role of this final cue has not been extensively studied in songbirds, but
there is some evidence to suggest that European starlings are sensitive to
the sequence of motifs within familiar song bouts (Gentner and Hulse
1998).
For species in which males sing multiple songs, the four mechanisms
outlined above may not be mutually exclusive. There is no a priori reason
to believe that vocal recognition in a single species relies on individual
variation coded in only a single dimension, nor is there any reason to
suspect that all species of songbirds use the same recognition strategies.
Given the approximately 4,500 different species of songbirds—each singing
acoustically distinct songs and the occurrence of vocal recognition in a wide
range of behavioral contexts, it is likely that vocal-recognition information
is coded at multiple levels throughout a songbird’s repertoire (Braaten
2000).
3.3.3. Laboratory Studies
Given the likely diversity of vocal-recognition behaviors across songbird
species, it is reasonable to consider whether there are corresponding peripheral perceptual specializations among songbirds that in theory might
provide an “open channel” of communication within a species while limiting confusion across species. For instance, different species might concentrate the spectral energy with their songs in defined spectral bands. This
hypothesis is supported by several observations of species-specific advantages during operant discriminations of multiple conspecific and heterospecific songs in several different species (Sinnott 1980; Okanoya and
Dooling 1990; Cynx and Nottebohm 1992; Dooling et al. 1992). However,
the overwhelming data from psychophysical studies of hearing in birds indicate that most basic sensory processing capabilities (e.g., frequency sensitivity) are conserved across songbird species (Dooling et al. 2000). Thus, it
appears that biases for the discrimination of species-specific vocalizations,
and hence mechanisms for vocal recognition, result from evolutionary or
ontogenic changes in central processing structures. This inference is consistent with the more general assumption that the cognitive processes underlying vocal recognition take the neural representation of acoustically
complex signals (i.e., song) as their input. Recent laboratory studies of
European starlings have addressed these questions by determining more
precisely the form of the acoustic signal controlling recognition in this
species.
Male starlings tend to present their songs in long episodes of continuous
singing referred to as bouts. Song bouts, in turn, are composed of much
smaller acoustic units referred to as motifs (Adret-Hausberger and Jenkins
1988; Eens et al. 1991), which in turn are composed of still smaller units
358
T.Q. Gentner and D. Margoliash