Birdsong Flashcards
What is birdsong? Uses
Vocalisation of more than one note for communication
Passerine are majority users
Used to find a mate and defend territory
Species-specific, repertoire variable
How was it researched?
Thorpe in 50s developed sonograph to record and ‘see’ it
Describe note, syllable and phrase
Note: individual sound
Syllable: unit of organization for a sequence of sounds
Phrase: group of syllables
Describe Thorpe’s experiment in ‘54
Isolated yound male chaffinches
Some played tape recordings of chaffinch song, others had none
Recorded vocals when adults
Results of Thorpe ‘54
Those raised with normal songs copy tutor well
Bird raised in acoustic isolation had simple song, suggesting there is an innate song which is modified by tutor
What happens when birds only exposed to tutor when mature?
Develop abnormal songs.
Meaning that there is a critical period for learning
What are the stages of song development?
Sensory phase (listen to tutor) Sensorimotor phase (subsong: soft, variable rambling syllables) and (plastic song: rehearsal, becomes like tutor song) Crystallised: song has correct volume, duration and syllables etc. - no further change
Difference between white crowned sparrow and zebrafinch learning
Sparrow is a seasonal closed learner (breeding season in spring, sing during this, song crystallised by next spring)
Zebrafinch is age limited learner (breed all year, critical period from 0-60 days. Sensory and sensorimotor overlap)
Describe learning of the canary
Open ended learner
Breeds in spring, learns new song each year (new sensory period?)
How can sensory phase be extended?
Environment: longer breeding season on coast
Lack of tutor
Presence of live tutor
What did Marler and Peters ‘81 do?
Analysed plastic phase syllables in sparrows 200 syllables total in plastic phase 32% copies of tutor 18% variations of tutor 50% invented
Result of swamp sparrow having 2 tutor songs
Combine them into novel song
Why are new songs only 32% imitation?
Overproduction of syllables in plastic phase leads to loss of them in crystallisation phase. Adult swamp sparrow song 45 syllables
Trying out different sounds?
What affects learning of tutor song?
Innate preference for own species (change in HR even in birds not previously exposed to song)
Preference for visible tutor (sparrow copies a finch in preference to tape of conspecific)
Describe Marler and Peters ‘77
Birds reared in isolation
Fledglinds 20-60 days) exposed to taped songs of both swamp and song sparrows
Swamp always preferred conspecifics
Song preferred foreign 20% of time
Results of Marler and Peters ‘77
Swamp sparrows recognised syllabled, not syntax
Song recognise syllables, syntax and tempo (would learn foreign syllables if in specific syntax and tempo) - has innate template
What does and isolate’s song retain?
Duration Tonality Freq rance Repertoire size (innate template)
Result of deafening bird
Can’t perform song
Auditory feedback required to match singing to template
Template part innate and learned
How is sound produced in birdsong?
Air comes from air sacs, body wall muscle expels it
Air movement cause tympaniform membranes to vibrate.
Internal and external syringeal muscles alter tension of tympaniform membrane to change freq
Evidence for lateralisation
Sectioning of left hypoglossal nerve causes song impairment.
Sectioning of right has little effect
Differing lateral dominance between species
Left: Canary, Java Sparror
None: Swamp sparrow
Right: Zebrafinch
(canary can recover by transferring song control to other half of syrinx)
Components of song production pathway
Higher vocal centre -> RA -> Respiratory control and nXlls
Anterior forebrain pathway
Critical for song learning
Intermediate route between HVc and RA
Why can canaries re-learn?
Open-ended learners
Lesion of left HVc causes re-learning in right HVc
Effects of lesion in RA
Also disrupts singing, showing it is also involved in song production
Where are song selective neurones located? Where do they project to?
Located in HVc, project to RA and area X
Active when hearing own or conspecific song - encoding song recognition
HVc and RA activity around singing
Active just before and during
Artificial stimulation causes phrase advance (showing role in CPG)
When does this pathway become functional?
During sensorimotor phase in zebrafinches, suggesting use in song production, not template forming
Summarise song production pathway
HVc -> RA -> nXlls and resp. control
Used in song production
HVc lesions disrupt
Anterior forebrain pathway consists of
HVc -> area X -> DLM -> LMAN -> RA
Effects of LMAN lesion in young and mature zebrafinch
Young: disrupts singing when mature
Mature: no effect
AFP involved in learning but not singing
When does AFP become active in zebrafinch?
Sensory phase
Role in learning templates
Functions of the two pathways
Song production path: song production
Anterior forebrain pathway: learning template
Variables affecting amount of singing
Gender, species and season
Linked to testosterone levels and size of song nuclei (HVc, RA and LMAN)
Effects of testosterone levels in canaries
Varies throughout year
Number of syllables increases with test levels
Effects of castration and HRT ect.
Castrated males fail to develop adult song
Synthetic test given to females causes them to sing
Castrated swamp sparrows sing if given HRT
Effects of HVc size on repertoire size
Positive correlation for a range of species
Difference in HVc size in male canaries from spring to autumn
Almost twice the size in spring (HVc: 99% larger, RA: 76% larger)
Effects of test treatment on female nuclei
Increases size of HVc and RA and causes them to sing
What is the reason for the increase in HVc size during sensory phase?
Increased number of synapses. New neurones forming
No new ones in sensorimotor phase
Suggests most plasticity occurs in sensory phase, particularly in AFP when template song formed
