Bird song

1
Bird song

• MSc ACSB module 2005/06
• Session 9

2
How bird song is used

• Territorial proclamation territorial defence,
  mate attraction
• Oscines (song birds) learn song in non-oscines,
  the whole vocal repertoire innate
• Learned basis may parallel learning of language
  but also consider function of learning, and
  neural control of song

3
Chaffinch Song (Thorpe)

• Songs of normal single isolate group isolate
  tutored from tape with end-part spliced into
  middle
• Learned variations in song in different males
• Learned over first year, even from tutor-tape
  isolation-reared song much simplified

4
Chaffinch song learning

• Learned during critical period (now sensitive
  period) closed-ended learning
• Proper song not produced without this experience,
  but not standard unconstrained learning will
  only learn own species song, very rarely a
  foreign element
• So constraints on learning Lorenz spoke of the
  innate schoolmarm
• What kind of genetic instructions produce this
  constrained learning, and why

5
White Crowned Sparrow song

• White crowned sparrow songs vary with locality
  around San Francisco bay
• Dialects learned during a males early
  post-fledging life (to 50 days of age)
• After this point, migrants start to travel south
  through region and birds no longer hear just
  local dialect

6
Why have a flexible learned signal which other
groups hard-wire?

• Cant be because complex song is too hard to
  achieve by hard-wiring
• Time of end of sensitive period in WCS suggests
  that learning designed to maintain dialect-system
• Nottebohm on Chingolo song types stable over
  vast areas of flat pampas, but changes rapidly as
  altitude increases on hills. ?Ensures that genes
  adapting to higher-altitude environment are not
  diluted by breeding outside the local population,
  i.e. with plains-birds.

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Parallels with language?

• Nottebohm (72) drew tentative parallels with
  human languages may also be important to
  constrain mate choice within group
• Baker found some dialect-linked differences in
  WCS gene frequencies, and reduced gene flow
  between neighbouring populations
• May influence area where birds settle where the
  local dialect is the one they heard when young

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Is emphasis on dialects misdirected?

• Jenkins (1985)
• Baker Cunningham reify dialect and then seek
  a function for it, whereas the key evolutionary
  question in this field is, Why did song learning
  evolve?
• We cannot hope to discover what birds do learn
  or re-learn in the wild if our experiments deny
  them the basic motivating stimulus for learning
  competition for resources
• Gaining a territory requires a bird to stand
  its ground, stake a claim, and attack males
  competing for the same mate. What do birds learn
  under these conditions, and when do they stop
  learning

9
Nowicki Searcy Developmental stability

• Animals differ in developmental stability
  extent to which good genetic constitution buffers
  them from shocks which could influence
  development during critical phases of growth
  (e.g. measured by FA)
• NS emphasize role of songs in revealing male
  quality females prefer large repertoires, etc.

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Developmental stability (2)

• Song repertoire size, copying accuracy, etc., may
  depend on growth of structures such as HVC during
  periods of development in which nutritional and
  other stresses can occur.
• Song repertoire, copying accuracy therefore
  provide females with index of males
  developmental stability in face of stressors

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Developmental stability (3)

• Studies of e.g. food restriction do show effects
  on song characteristics, e.g. copying accuracy
• So an open rather than closed instruction-set
  for song development could permit bird song to
  provide a long-distance index of male quality
• Is there any parallel with human language
  development?

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Variety in song learning

• This idea cant account for all variations in
  detail
• Cardinals both MF sing, sensitive periods 71d
  F, 187d M Ms will be able to included phrases
  learned where settle, F keep to natal dialect
• Many learn local song, or taped song of their own
  (but not from other) species - e.g. White Crowned
  Sparrow but Zebra finch learns only (foster-)
  fathers song
• Mynah mimics human speech Lyrebird mimics many
  sounds

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Studies of the song-learning process (1)

• Early sensitive period (50d in WCS), later
  sub-song, plastic song, crystallised song
• End of sensitive period may depend on relevant
  input speeded if hear suitable song, delayed if
  deprived

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Song learning (2)

• Parsing syllables in song sparrow song learning
  ABCDE structure can be reconstructed if tutored
  with disconnected syllable-pairs that never
  reveal the whole order, e.g. DE, AB, CD, BC
• If present ED, BA, DC, CB, reconstruct EDCBA
• If present individual syllables rather than
  pairs, final song bears little resemblance to
  normal song structure

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Song learning (4)

• Song sparrow complex song
• Swamp sparrow simple trill
• White crowned sparrow intermediate
• Used in cross-learning studies

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Cross-learning

• Nature of learning-template reflects
  song-syllables and song-structure
• Swamp Sparrow learns Swamp-S syllables even if
  Song-S structure
• Song Sparrow learns Song-S syllables in Swamp-S
  structure (trill) AND Swamp-S syllables if put
  into Song-S structure

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Song control systems

• Crystallised song may not be crystallised
• Zebra finch syllables lose form after deafening,

NIf

• No loss of form if deafen LMAN lesion
• LMAN flags discrepancy (heard song ? template),
  sends instruction to vary song
• Deafen -gt mismatch -gt signal plastic Deaf
  LMAN-X -gt no signal -gt remains stable
• Okanoya NIf -gt complex syntax in domestic
  Bengalese finch compared to wild ancestor

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References

• Hauser (1997) Evolution of communication. Ch.
  5.2.1
• Brainard Doupe (2004) Nature, 417, 351-358
• Beecher Brenowitz (2005) TREE, 20, 143-149
• Brenowitz Beecher (2005) TINS, 28, 127-132
• Marler (1981) TINS 4, 88-94
• Nowicki Searcy (2004) Ann. NY Acad. Sci. 1016
  704-723
• Okanoya (2004) Ann. NY Acad. Sci. 1016 724-735