Birdsong Acquisition

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Birdsong Acquisition
Irina Gruzinova ECOL 484
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Birdsong Acquisition Innate/Learned Behavior

• Great vocalization diversity and generally
  species-specific song patterns.
• Implies innate predisposition to learn
  conspecific song.
• It has been established that learning is crucial
  to birds singing ability.
• Birds deafened or held in auditory isolation as
  juveniles do not develop normal songs. (Brainard
  2006)
• Presence of geographically restricted dialects
  within species. (Naguib 2006)
• Learning stages
• Subsong
• Plastic Song
• Crystallization Most birds reach an age where
  song plasticity is reduced.

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a) Adult zebra finch song. b) Song of a zebra
finch, tutored by the bird in a at an early stage
of sensorimotor learning. c) Song of the same
bird close to song 'crystallization'. Note the
similarities between this bird's song and that of
its tutor. d) Song of a zebra finch raised in
acoustic isolation. Note the overall simplicity
of this song, but its general similarity of
structure to other zebra finch songs. (Brainard
2002)
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Birdsong Acquisition Nature vs. Nurture

• Most birds are predisposed to learn their
  species-specific or conspecific pattern.
• Most birds will preferentially learn conspecific
  song although some are capable of copying
  heterospecific song, especially if its the only
  audible song. (Marler 1988)
• Birds raised in acoustic isolation will sing
  simple songs that contain some species-specific
  structure. (Konishi 1985)
• Much variability of learning mechanisms among
  species. Species seem to vary in their dependence
  on innate and learning processes during song
  acquisition.
• Species specific-song and mimicry

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Variability in Learning Mechanisms open-ended
vs. closed-ended learners onset of
crystallization varies
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Birdsong Acquisition Nature vs. Nurture

• Birdsong was played to male song sparrows
  collected as nestlings in Durham, North Carolina
  in a study designed to discover how exposure to
  within-song variation influences the song
  learning process. (Nowicki, 1998)
• Young males that were tutored with invariant song
  models and males tutored with variable songs did
  not differ in any measure of how well they
  learned and in the expression of within-song
  variation in their own adult songs, demonstrating
  that within-song variation is not a learned
  feature.
• Birds that were tutored with both invariant and
  variable models preferentially copied variant
  song type.
• This finding of intrinsic preference for variant
  songs supports the fact that song acquisition of
  song sparrows is partly dependent on innate,
  genetic factors. (Nowicki, 1998)

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Birdsong Acquisition Nature vs. Nurture

• Ichard Braaten et al. (2006) exposed young male
  and female zebra finches to 14 zebra finch and 14
  starling songs presented from a loudspeaker to
  explore whether zebra finches prefer conspecific
  over heterospecific songs.
• The recognition memory for these songs was tested
  in a unique fashion. The birds were trained to
  discriminate between familiar and novel songs.
  (Braaten et. al, 2006)
• Birds were conditioned to hop to the feeder perch
  upon hearing 16 familiar songs through the
  presentation of food rewards. If the birds
  responded to a novel song, the houselight was
  turned off for 15 s as a punishment.
• Following discrimination training, familiar and
  novel probe songs were played without
  reinforcement to test the recognition memory for
  songs.
• The birds responded to the presentation of
  familiar conspecific and heterospecific songs
  equally well, so they did not prefer conspecific
  over heterospecific songs. (Braaten et. al, 2006)
• Zebra finches song acquisition is more dependent
  on learning and imitating than innate song
  recognition.

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Auditory Feedback Theory

• Song development depends both on listening to a
  tutor and practicing the tutors songs.
• Birds engage in motor skill learning, guided by
  performance-based feedback. (Naguib 2006)
• Compare their own vocalizations to a memorized or
  innate song pattern in order to attain a better
  imitation. (Brenowitz 2005)
• Why birds that are deafened as juveniles will not
  develop normal songs. (Brainard 2005)
• Adult birds also need to hear and practice their
  song, since deafening of adult zebra finches
  caused their song to deteriorate slowly. However,
  the degree of song deterioration after hearing
  loss is much less severe in adulthood than in
  juveniles. (Brainard 2005)

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Auditory Feedback Theory

• Deregnaucourt et. at (2005) studied the effect of
  sleep on zebra finch song development.
• Researchers tutored the birds by playing song
  recordings, and recorded the entire song
  development of all birds. (Deregnaucourt et. at
  2005)
• The deterioration of song structure after sleep
  was identified during the plastic stage,
  followed by improvement in similarity to the
  tutored song after morning singing.
• The song of 8 deafened adult birds was analyzed.
  The post-deafening deterioration in adult birds
  was similar to that observed in young birds after
  sleep. So, the lack of song replay and rehearsal
  can explain song deterioration of song structure
  after sleep, proving that auditory feedback is
  necessary to sustain and improve song structure.
  (Deregnaucourt et. at 2005)
• Birds that exhibited stronger post-sleep
  deterioration during development achieved a
  better final imitation.
• Periodic increases in plasticity give birds
  repeated opportunities to reshape previously
  learned songs and to correct inappropriately
  memorized material (Deregnaucourt et. at 2005)

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Auditory Feedback Theory

• The following study competed by Michael Beecher
  et. al (2006) compared how much young song
  sparrows learned from two kinds of adult song
  tutors one with whom the subject interacted
  vocally, and one whom the subject only overheard
  singing with another young bird. (Beecher et. al,
  2006)
• Song sparrows learned more than twice as many
  songs from an overheard tutor than from an
  interactive experience with a tutor. (Beecher et.
  al, 2006)
• So, young birds learn more by eavesdropping than
  by direct interaction. (Beecher et. al, 2006)

• Auditory feedback theory stresses the importance
  of rehearsal and the comparison of own
  vocalizations to the utterances of the tutor, so
  these results are contradictory.