Birdsong Acquisition Irina Gruzinova ECOL 484

Birdsong Acquisition: Innate/Learned Behavior Great vocalization diversity and generally species-specific song patterns.  Implies innate predisposition to learn conspecific song. It has been established that learning is crucial to birds’ singing ability.  Birds deafened or held in auditory isolation as juveniles do not develop normal songs. (Brainard 2006)  Presence of geographically restricted dialects within species. (Naguib 2006)  Learning stages Subsong Plastic Song Crystallization: Most birds reach an age where song plasticity is reduced.

a) Adult zebra finch song. b) Song of a zebra finch, tutored by the bird in a at an early stage of sensorimotor learning. c) Song of the same bird close to song 'crystallization'. Note the similarities between this bird's song and that of its tutor. d) Song of a zebra finch raised in acoustic isolation. Note the overall simplicity of this song, but its general similarity of structure to other zebra finch songs. (Brainard 2002)

Birdsong Acquisition: Nature vs. Nurture Most birds are predisposed to learn their species-specific or conspecific pattern.  Most birds will preferentially learn conspecific song although some are capable of copying heterospecific song, especially if it’s the only audible song. (Marler 1988)  Birds raised in acoustic isolation will sing simple songs that contain some species- specific structure. (Konishi 1985) Much variability of learning mechanisms among species. Species seem to vary in their dependence on innate and learning processes during song acquisition. Species specific-song and mimicry

Variability in Learning Mechanisms open-ended vs. closed-ended learners onset of crystallization varies

Birdsong Acquisition: Nature vs. Nurture Birdsong was played to male song sparrows collected as nestlings in Durham, North Carolina in a study designed to discover how exposure to within-song variation influences the song learning process. (Nowicki, 1998) Young males that were tutored with invariant song models and males tutored with variable songs did not differ in any measure of how well they learned and in the expression of within-song variation in their own adult songs, demonstrating that within-song variation is not a learned feature. Birds that were tutored with both invariant and variable models preferentially copied variant song type. This finding of intrinsic preference for variant songs supports the fact that song acquisition of song sparrows is partly dependent on innate, genetic factors. (Nowicki, 1998)

Ichard Braaten et al. (2006) exposed young male and female zebra finches to 14 zebra finch and 14 starling songs presented from a loudspeaker to explore whether zebra finches prefer conspecific over heterospecific songs. The recognition memory for these songs was tested in a unique fashion. The birds were trained to discriminate between familiar and novel songs. (Braaten et. al, 2006)  Birds were conditioned to hop to the feeder perch upon hearing 16 familiar songs through the presentation of food rewards. If the birds responded to a novel song, the houselight was turned off for 15 s as a punishment.  Following discrimination training, familiar and novel probe songs were played without reinforcement to test the recognition memory for songs. The birds responded to the presentation of familiar conspecific and heterospecific songs equally well, so they did not prefer conspecific over heterospecific songs. (Braaten et. al, 2006) Zebra finches song acquisition is more dependent on learning and imitating than innate song recognition. Birdsong Acquisition: Nature vs. Nurture

Auditory Feedback Theory Song development depends both on listening to a tutor and practicing the tutor’s songs.  Birds engage in motor skill learning, guided by performance-based feedback. (Naguib 2006)  Compare their own vocalizations to a memorized or innate song pattern in order to attain a better imitation. (Brenowitz 2005)  Why birds that are deafened as juveniles will not develop normal songs. (Brainard 2005)  Adult birds also need to hear and practice their song, since deafening of adult zebra finches caused their song to deteriorate slowly. However, the degree of song deterioration after hearing loss is much less severe in adulthood than in juveniles. (Brainard 2005)

Auditory Feedback Theory Deregnaucourt et. at (2005) studied the effect of sleep on zebra finch song development. Researchers tutored the birds by playing song recordings, and recorded the entire song development of all birds. (Deregnaucourt et. at 2005) The deterioration of song structure after sleep was identified during the ‘plastic’ stage, followed by improvement in similarity to the tutored song after morning singing. The song of 8 deafened adult birds was analyzed. The post-deafening deterioration in adult birds was similar to that observed in young birds after sleep. So, the lack of song replay and rehearsal can explain song deterioration of song structure after sleep, proving that auditory feedback is necessary to sustain and improve song structure. (Deregnaucourt et. at 2005) Birds that exhibited stronger post-sleep deterioration during development achieved a better final imitation.  Periodic increases in plasticity give birds repeated opportunities to reshape previously learned songs and to correct inappropriately memorized material (Deregnaucourt et. at 2005)

Auditory Feedback Theory The following study competed by Michael Beecher et. al (2006) compared how much young song sparrows learned from two kinds of adult song tutors: one with whom the subject interacted vocally, and one whom the subject only overheard singing with another young bird. (Beecher et. al, 2006) Song sparrows learned more than twice as many songs from an overheard tutor than from an interactive experience with a tutor. (Beecher et. al, 2006) So, young birds learn more by eavesdropping than by direct interaction. (Beecher et. al, 2006) Auditory feedback theory stresses the importance of rehearsal and the comparison of own vocalizations to the utterances of the tutor, so these results are contradictory.