The biological basis of bird song production'

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The biological basis of bird song production.

• Bird song facts
• There are about 4000 species of song birds each
  of which usually produce 1 to many bird songs.
• In all studied cases adult song has been shaped
  by learning.
• In most cases it is the male of the species that
  produces song,
• Females typically produce little or no
  sound/song.
• Males within any single species tend to sing
  highly similar sets of songs.
• There can be dialectic variations in different
  geographic regions for a given song.
• In some cases, dialectic variations of a song
  within a region will change over time (i.e.
  across generations).

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Three most common species used in the study of
song production and learning
White Crowned Sparrow
Zebra Finch
Canary

• Function of bird song
• Attract mates
• Advertise health
• Genetic quality
• Sync courtship behaviors
• Maintenance of pair bond
• Establish/defend territory
• Flock control
• Predator alarm
• In flight flock movement
• Parent offspring communication

Chaffinch A historically significant species
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• The syrinx The song machine
• Located at the point where the trachea branches
  into the two primary bronchi.
• Sound is generated when
• Air from air sacs is forced through the bronchi
  syrinx
• Air vibrates as it passes through the narrow
  passageways between the external labia the
  tympanic membrane.
• Because there are 2 separate passageways and
  membranes, some birds are able to generate
  multiple sounds harmonics at the same time

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Studying the song
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Parts of a bird song
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Song learning Modern experimental studies of
song learning in birds began in the 1950's in
laboratory of W.H. Thorpe.  Birds that were
hand-reared from an early age without hearing the
normal adult song of its species, a simplified
"isolate" song is produced.
Isolate songs are highly variable within a
species but tend to be related in some
rudimentary way with a normal song.
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A song developed by a male white-crowned sparrow
that was tutored early in the first 2 months of
life.
Here is the tape-recorded song he was tutored
with. 

• Song learning facts
• Juveniles need adult tutoring to produce normal
  song.
• There is variability across individual songs
  this may be the basis of dialect formation.
• Juveniles prefer/learn songs of their species
  better than they learn other species songs.

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Gene environment interactions Within species
preferences for song learning

• Given a choice there is an innate preference for
  ones own species song
• True even at the subspecies level.
• If wrong song is paired with visual cues
  learning wrong song is enhanced

Baptistia and Petrinovich
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Within species preferences for song learning
Experiment 2 between species ONLY tutor
Conclusion White Crowns will learn a song if
their own species is not present they will learn
what is available
Baptistia and Petrinovich
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Stages of song development (learning)

• Normal song development proceeds through a series
  of stages 
• Sensory Young male memorize songs of one or more
  adult birds. 
• Sensitive phase a developmental window where
  babies listen and learn (species specific but
  10-50 days post hatch). 
• Sensory motor Vocal production begins during or
  soon after the sensitive phase when the male
  begins subsong. 
• Subsong has been compared to babbling in human
  infants. 
• Birds that do not learn to sing do not produce
  subsong.  

Example subsong babbling performed by a 240
day old white-crowned sparrow.
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Stages of song development Sensory motor (cont.)

• Subsong gives way to plastic song organized
  imitation songs
• The first evidence of imitations of tutor songs
  appears in the male's singing.  
• Plastic song, imitations are often incomplete. 
• Developed songs tend to be "hybrid" songs
  composed of parts of two or more different tutor
  songs.  
• Overproducing singing more imitations than
  eventually appear the final crystallized song. 
• Crystallized songs can change over time.

• Stages are
• Species specific
• Dependent on reproductive cycle
• Some are plastic and dependent on environmental
  circumstances.

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Stages of song development
Example Plastic songs by a 260 day old WC
sparrow containing three different songs. The
three tutors that the male memorized during the
sensitive phase are shown above, and are
connected by arrows to the young male's
imitations. 
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Stages of song development

• Crystallized song The emergence of the adult
  song occurs through the process of selective
  attrition of syllables from overproduced plastic
  song repertoire
• Mediated by hearing the song of the tutor and
  auditory feedback. 
• Cochlear ablation studies demonstrate that
  auditory feedback of ones own song is critical

Example The first song is the tutor, the second
is the juveniles rendition of the matching song
type.   This male has stopped singing his
imitations of Tutors 2 3, (above) and will
retain his crystallized imitation of Tutor 1. 
Selective attrition may lead to vocal dialects,
in which neighboring males sing very similar
songs that differ from the songs at other
locations.
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Dialectic differences in WC sparrow

• Factors
• Environment
• Error and learning culture
• Genetic drift with natural selection