Calibration of song learning targets during vocal ontogeny in swamp sparrows, Melospiza georgiana
Song learning in songbirds often includes an extended sensorimotor phase, in which birds gradually refine their vocal output to produce accurate copies of previously memorized song models. Increasing accuracy of song model reproduction during this phase occurs as birds refine the neural substrates that underlie vocal control, and as they develop proficiency with the vocal apparatus. We here test the hypothesis that sensorimotor learning also provides birds with an opportunity to calibrate their vocal learning targets, in the event that a bird's own vocal proficiency differs from that required to successfully reproduce song models to which it is exposed. We tutored hand-reared male swamp sparrows with song models that we manipulated to vary in how challenging they would be to reproduce, and then tracked patterns of song development. The calibration hypothesis was supported by two lines of evidence. First, we found that copies of manipulated models underwent comparatively large-scale modifications in syntax and note composition over development, in directions consistent with expectations about motor proficiency relative to the structure of learned models. Second, we found that birds tended to retain selectively, in their crystallized repertoires, song types that appeared to be comparatively easy to produce. Our results are consistent with an 'active' model of song learning, and also suggest a specific mechanism by which learning can act as a creative or a stabilizing force in song evolution. © 2004 The Association for the study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
Podos, J; Peters, S; Nowicki, S
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