theses where appropriate. We also describe evidence of the vocal learning
process when that information is available. We briefly describe vocal learning of group signatures in taxa not covered in case studies in Tables 4.1
(birds) and 4.2 (mammals).
3.1. Birds
3.1.1. Oscines—Chickadee Flock Signatures
Black-capped chickadees (Parus atricapillus) associate in small, fairly stable
flocks of four to eight birds during nonbreeding months. Breeding pairs
form within these flocks and defend breeding territories (Ficken et al. 1981).
Flocks defend shared feeding territories. The composition of flocks is relatively stable throughout each year, but changes from one year to the next
due to adult mortality and recruitment of dispersing juveniles (Weise and
Meyer 1979; Nowicki 1989). Flock mates are probably not closely related
to one another, but the degree of relatedness is unknown.
Song and call distinctions are not particularly clear in chickadees, and the
complexity of some call types exceeds that of song. Many call types are
given by both sexes (Ficken et al. 1978). Here, we focus on two call types
that have been well-studied: the gargle and the chick-a-dee. The gargle is a
variable series of two to nine notes given primarily by males (Ficken et al.
1978; Ficken and Weise 1984). Gargles are given in agonistic encounters
between flock mates, during territorial encounters, and prior to copulation.
They are not used to advertise flock territories but rather to defend those
territories against intrusion and to maintain dominance hierarchies within
flocks (Ficken et al. 1978). The chick-a-dee call consists of four note types
(Fig. 4.4A). Each note type is given a variable number of times in an invariant sequence: A, B, C, D. Chick-a-dee calls are given by both sexes throughout the year and function as contact calls—to coordinate movements of
pairs and flocks (Ficken et al. 1978; Nowicki 1983) and facilitate recognition of flock mates (Nowicki 1983). Birds also give chick-a-dees during
interflock encounters and when mobbing predators. Flocks differ in call
characteristics, primarily of the D note, and calls of individuals within flocks
are convergent (Mammen and Nowicki 1981; Nowicki 1989). Recognition
of flock mates could be based on both flock and individual differences
(Nowicki 1983).
Observational and experimental evidence for vocal learning supports the
role of social modification and, to a lesser extent, learned acquisition of
both gargle and chick-a-dee calls. Social modification is implicated in gargle
development on the basis of observational data on dialect variation (Ficken
and Weise 1984; Ficken et al. 1985; Ficken and Popp 1995; Hailman and
Griswold 1996). Hand-reared birds produced calls similar to individuals
with which they were raised and different in subtle ways from free-living
birds (Ficken and Weise 1984). The chick-a-dee call is better studied and
suggests both learned acquisition and social modification. Observational
4. Comparative Vocal Learning
169
process when that information is available. We briefly describe vocal learning of group signatures in taxa not covered in case studies in Tables 4.1
(birds) and 4.2 (mammals).
3.1. Birds
3.1.1. Oscines—Chickadee Flock Signatures
Black-capped chickadees (Parus atricapillus) associate in small, fairly stable
flocks of four to eight birds during nonbreeding months. Breeding pairs
form within these flocks and defend breeding territories (Ficken et al. 1981).
Flocks defend shared feeding territories. The composition of flocks is relatively stable throughout each year, but changes from one year to the next
due to adult mortality and recruitment of dispersing juveniles (Weise and
Meyer 1979; Nowicki 1989). Flock mates are probably not closely related
to one another, but the degree of relatedness is unknown.
Song and call distinctions are not particularly clear in chickadees, and the
complexity of some call types exceeds that of song. Many call types are
given by both sexes (Ficken et al. 1978). Here, we focus on two call types
that have been well-studied: the gargle and the chick-a-dee. The gargle is a
variable series of two to nine notes given primarily by males (Ficken et al.
1978; Ficken and Weise 1984). Gargles are given in agonistic encounters
between flock mates, during territorial encounters, and prior to copulation.
They are not used to advertise flock territories but rather to defend those
territories against intrusion and to maintain dominance hierarchies within
flocks (Ficken et al. 1978). The chick-a-dee call consists of four note types
(Fig. 4.4A). Each note type is given a variable number of times in an invariant sequence: A, B, C, D. Chick-a-dee calls are given by both sexes throughout the year and function as contact calls—to coordinate movements of
pairs and flocks (Ficken et al. 1978; Nowicki 1983) and facilitate recognition of flock mates (Nowicki 1983). Birds also give chick-a-dees during
interflock encounters and when mobbing predators. Flocks differ in call
characteristics, primarily of the D note, and calls of individuals within flocks
are convergent (Mammen and Nowicki 1981; Nowicki 1989). Recognition
of flock mates could be based on both flock and individual differences
(Nowicki 1983).
Observational and experimental evidence for vocal learning supports the
role of social modification and, to a lesser extent, learned acquisition of
both gargle and chick-a-dee calls. Social modification is implicated in gargle
development on the basis of observational data on dialect variation (Ficken
and Weise 1984; Ficken et al. 1985; Ficken and Popp 1995; Hailman and
Griswold 1996). Hand-reared birds produced calls similar to individuals
with which they were raised and different in subtle ways from free-living
birds (Ficken and Weise 1984). The chick-a-dee call is better studied and
suggests both learned acquisition and social modification. Observational
4. Comparative Vocal Learning
169