Bird Song and Learning

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Bird Song and Learning

• Parrots, Humming Birds and Song Birds (taxonomic
  order, Passeriformes)
• Passerines divided into Oscines that learn their
  song (46 of the 9,000 bird species) and
  Suboscines that have an innate song (12)

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Sonogram of a Suboscine
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Darwins Finches

• Galapagos Islands Sympatric speciation
• Seed eaters versus insect eaters
• Heavy squat beaks for cracking seeds, versus long
  narrow beaks for getting insects
• Low frequency for large beaks, high frequency
  complex song for long beaks

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How is Song Learned?

• Peter Marlers work on white crowned sparrows
• Raised in isolation WCS do not sing a species
  typical song
• Tape playback in lab raised WCS

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Data Based on Tape playback

• Innate bias for species specific song
• Memory stored between days 10 and 50 post-hatch
  (critical period)
• Produce song at 150 days post-hatch
• Auditory feedback for complete song at 200 days
• Irreversible--crystallized song

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Zebra Finch Song in Normal and Deafened offspring
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LaboratoryTape Playback Theory of Song Learning
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Problems With the Tape Playback Theory

• Babtista and Petrinovich observed WCS in nature
  singing another species song
• Suggest that the social stimulation of a live
  tutor is important
• Found 10 to 50 day critical period is too short,
  alien species song may be learned, song may be
  modified as an adult

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Neural Control of Song

• Sex-Determining Chromosomes XX female, XY
  male in mammals, in birds ZW female and ZZ
  male
• W chromosome has fewer genes than Z
• Females dont sing, only males sing
• Females do memorize song, but their brain doesnt
  develop to allow production

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Steps in the Development of Males Brain for Song
(Neuroethology)

• Testes produce testostrerone
• Brain centers such as the higher vocal center
  (HVC) are sensitive to testosterone
• Males develop song centers females dont

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Zebra Finches (Taeniopygia guttata) Male and
female and home range
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Song Storage (memory)

• Hear and see tutor
• Stimulation of cells in the IMAN area of the
  brain and area X
• Genes in neuron are turned on
• New production of proteins
• Reshaped neuronal structure
• IMAN area is much larger in oscines than in
  suboscines

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Production of Song

• Syrinx is like the larynx
• It is connected to the nXIIts which receives
  input from RA and HVC
• Lesions of the RA or HVC or their connections
  produce a deficit in song
• The size of the RA is greater in males that
  females

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Neural Changes that Produce song

• Selfstimulation of rough version of song
• The gene ZENK is activated in area X
• Altered proteins as song is perfected
• Once crystallized ZENK activity subsides
• Permanent neural circuitry is in place

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Why Do Birds Sing?

• Kin Recognition Who is in the family?
• Species recognition Who should I mate with?
• Neighbor recognition Good fences make good
  neighbors
• Territory marker and mate guarding
• Mate selection Good singers make good lovers

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Song and Mate Selection

• Louder, longer and more complex songs signal good
  genes and good development
• A strong singer is less likely to have parasitic
  infections, a heritable trait
• Strong singers (large HVC) had a better diet
  during early development

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Time spent sitting near the location of a tape of
a male starling
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Two weeks of free food (control) or two weeks of
70 (experimental)
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Females removal results in increased singing
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Song as an Honest Marker

• Physical or behavioral traits have a cost
• Conspicuous to predators
• Energetic costs
• Handicap principle
• Females pay attention to the song quality

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Female Sexually Receptivity Displays to Different
Songs
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Song Learning as an Adult

• Cowbirds (Molothrus ater) are reproductive
  parasites
• Female lays eggs in another species nest
• Since the hatchlings are deprived of conspecific
  song, it was thought their song was unlearned
• Male cowbirds raised in isolation do sing a
  potent song

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Learning in Cowbirds

• Male sings one of his songs, female wing
  strokes to indicate approval
• Male repeats song several times after wing
  stroking
• Beak gapes also used as positive feedback

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Female Cowbird
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Male Cowbird
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Context Specific Male Song

• Dominant males sing the most potent songs
• Females agree on which are potent and which are
  not
• Subordinate male may be attacked and killed if he
  sings too potent of a song
• Very different from white crowned sparrows

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Some General Conclusions About Song Learning

• Learning can occur in the absence of performance
  (WCS, Zebra Finches)
• Learning can occur along with performance
  (Cowbirds)
• Practice and feedback are needed to perfect the
  song
• Learning may be restricted to certain
  developmental periods (critical or sensitive
  periods?)

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Conclusions Functional Aspects

• Marker of good health
• Sexually selected Males know when and how to
  sing, females respond in an appropriate way
• Species and kin identification
• Territorial boundaries
• Learning is a very useful adaptation

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Song Sparrow