Chapter 2: proximate and ultimate approaches to communication.

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Chapter 2 proximate and ultimate approaches to
communication.

• Proximate What systems contribute to song?
• genes, hormones, brain, auditory system
• Ultimate How and why did singing evolve?

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Why do birds sing?

• Males sing attract females
• Defend and define boundries of territories

Other Types of communication?
Warning of predators/ danger Communication with
young Communicate with each other
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White Crowned sparrow dialects
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Why would WCSs from different parts of CA have
slightly different songs?

• Genetic basis for song all normal males can
  sing.
• Environmental basis song components must be
  learned from other males.

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White crown sparrows learn calls within 50 days
of hatching

• Young hear males within district
• Adjust calls according to dialect they hear
• Gene basis for song envs basis for dialect

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WCSs have gene based system with social (env)
influence on final outcome.

• Brain changes 1st 50 days allow basic song
  components to be learned.
• 150 to 200 days later, final touches, slight
  changes occur
• 200 days, no further adjustments Exception??
  Mockingbirds, parrots, parakeet
• Why are these exceptions??

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The Nature Nurture argument
cockatoo
galah

• Is communication genetically based?
• Cockatiel vs galah study

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Galah, Cockatoo life history

• Both tree nesters -compete for tree cavities
• Sometimes lay eggs in the same nest
• Pink cockatoo larger, drives out galahs, keep
  eggs
• ?? Genes vs environment
• ?? gallah calls (genes) or cockatoo (env) for
  foster kids?

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Types of calls

• Begging calls
• asking for food
• Alarm calls
• Warn of danger
• Contact calls
• social
• Find a mate
• bonding

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Case Study methods

• Different Species - cross fostered
• Evaluate different types of calls in young

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Results of Cross Fostering

• Begging - galah
• Warning - galah
• Contact - cockatoo

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Results Contact Calls
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What is the significance of the cross
fostered galah calls?
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Zebra finch studies Fathers teach
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What are the underlying mechanisms for bird song?

• Gene system
• ZZ male ZW female
• Different genes
• Different development patterns
• Different hormones
• Different brains
• Female brains cant learn songs
• Unless manipulated w/ hormones

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Differences in males and females
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Gene expression in zebra finches

• Brain section stained to respond to Gene ZENK,
  thought to be responsible for song learning.
• White yellow areas correspond to area X.
• Shows gene ZENK proteins concentrated in Area X.

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How do male and female development and song
learning vary?

• Hormone differences based on genes
• Brain differences

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Testosterone responsible for differences in
ability to learn song

• Testosterone stimulates growth of neural circuits
  that allow song to be learned.
• Females dont have testes producing testosterone,
  no neural circuits for song learning.
• How do they communicate?
• Social contact, begging, alarm calls?
• Why is the lack of song an evolutionary
  advantage?
• So why do males have it?

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Brain Differences

• Male female
• Differences in the RA (arcopallium region)

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How do you manipulate song learning in the
laboratory?

• Artificial deafening (zebra finches
• Eastern Phoebe)
• Genetic deafening (zebra finches)
• Hormone manipulation (several species)
• Isolation experiments -(WCS)

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What are critical learning periods?

• 1 50 days after hatching, window of learning
  opportunity exists.
• Young must hear same species
• After 50 days, cannot learn song. Not silent,
  but not species specific song.

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Exceptions to the Rule The Eastern Phoebe

• Does not need to hear others to learn song.
• Significance??

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What parts of the brain are involved in song
learning?
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Brain function in song learning.

• Arcopallium
• nucleus of song production
• Higher Vocal Center
• main output region
• IMAN-nidopallium
• Song learning
• HVC
• song learning
• Area X
• song learning

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Evidence for brain function in song learning?

• HVC European warblers with better, more complex
  songs had larger HVC
• RA males have significantly larger area in
  response to ZENK gene in zebra finches
• IMAN zebra finch can sing song learned earlier
  but cant learn song if gone.

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Impact of social influences evolution of
variation based on social background Brood
parasites

• Cowbirds parasites raised by other songbirds
• ?? How do they hear their species call??

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Impact of social influences evolution of
variation based on social backgroundbarn
swallows vs cliff swallows

• Single (barn) vs Male female recognize
  individual calls in cliff but not barn swallows
• why evolve difference?

Barn solitary
cliff - colony
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What are the ultimate explanations for song
learning?

• Territoriality
• Female preference
• Communication
• other

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Several species gene based only
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Brains of song learners show similar
structure(parrots, warblers, hummingbirds)
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Territoriality
Males sing more if other males near
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Females respond to same species calls
Playback experiments with WCS females show they
prefer their own species to Dark eye juncos
(another species)
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Female preferences for song males evolve more
complicated songs

• European Starling Studies

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Female choice in song learning?

• Playback experiments show that birds prefer their
  own species and certain components of song.

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Proximate summary
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Ultimate Summary