1 / 18

Environmental Constraints on Song Structure

Environmental Constraints on Song Structure. Forests: pattern in amplitude modulation and spacing of sounds More attenuation of short wavelengths disrupts frequency modulation over distance Examples: Northern Cardinal, Carolina Wren Grasslands: pattern in frequency modulation

ismael
Download Presentation

Environmental Constraints on Song Structure

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Environmental Constraints on Song Structure • Forests: pattern in amplitude modulation and spacing of sounds • More attenuation of short wavelengths disrupts frequency modulation over distance • Examples: Northern Cardinal, Carolina Wren • Grasslands: pattern in frequency modulation • Examples: Eastern Meadowlark, Song Sparrow • Upward defraction of sound leads to early singing, singing from high perches, song flights

  2. Duets • Occurs 240 species in 44 families • 20+ species each shrikes, wrens, honeyeaters • Antiphonal singing = duets in which sexes alternate notes in what sounds like one song • Associated with jointly-held year-round territories, especially in the tropics • Possible function = territory defense female (she starts song), mate-guarding male (he adds) • Local example = Carolina Wren

  3. Elements of Song Learning • Innate template: neural image in brain determines what pay attention to • Sensitive period: modify innate template to produce permanent motor tape based auditory input during a particular period • Practice (song crystallization): during later period sing subsong, modify based on hearing self sing to produce adult song

  4. Experimental Evidence • Birds isolated during sensitive period sing unmodified template, even if surrounded by other singing birds as adults • Birds deafened after sensitive period sing subsong (no auditory feedback for practice) • Birds deafened as adults sing normal song, do not need to hear self sing to produce perfect song

  5. Variations in Song Learning • Specificity of template • Swamp Sparrow learns only syllables from own species, Song Sparrow sometimes learns syllables other species, mimics learn everything • Complexity of template • White-crowned Sparrow simple, differs adult song; Song Sparrow more complex, more like adult song

  6. Timing of sensitive period • Early, before practice • Later, overlaps with practice • Both early and later • Annual, modify song every year • How well copy what heard • Copy song units exactly • Copy syllables exactly, make own song units • Improvise and invent as well as copy

  7. Outcomes of Variation • Broad templates, inexact copying, long and late sensitive periods associated with large song repertoires • Narrow templates, exact copying, early sensitive periods associated with small song repertoires and stereotyped songs • Timing of sensitive periods often matches ecology to enable song matching

  8. Many sedentary species have fixed songs, early sensitive periods (after dispersal) Example: Marsh Wren

  9. Many nomadic species relearn songs yearlyExample: Sedge Wren

  10. Dialects in Birds • Regional differences in song • Some are sharp, distinct, persistent • White-crowned Sparrow example • Some are gradual, so that populations far apart sound the most different • Some may function to promote song matching, others may be accidental byproducts of the song learning system

  11. Elements Song Control System • HVC (High Vocal Center) in hyperstriatum and RA nucleus in corpus striatum are the song control centers • Connections here = innate template that is modified into motor program for song • New neurons, synapses form here during song learning, even in adults • TSM nucleus controls muscles of syrinx to produce song • TSM controlled by HVC and RA

  12. More Elements • L nucleus receives auditory input, provides feedback to song control centers • Provides input to modify template during sensitive period • Provides input during practice • Not involved in singing by adult birds • ICo nucleus in midbrain controls motivation to sing (when to sing, not what to sing)

  13. Hormonal Control • Hormones involved in seasonal, other longer term changes • Hormones bind to neurons in ICo to control seasonal changes in motivation to sing • Hormones involved in sensitive periods, control growth and other changes (based on learning) in song control centers

More Related