Our results suggest that, in chipping sparrows, intact hearing can influence the quality of male begging calls, auditory-sensitive vocal variability during food begging calls is the first step in a modification of vocal output that eventually culminates with vocal imitation.
In the present study, we also found that the structure of groans changed between years according male quality, inducing a modification of vocal cues to identity.
In this case, do quality-related changes to the acoustic structure of calls induce a modification of vocal cues to identity from year to year?
Do all these observed age and rank-related changes induce a modification of vocal cues to the identity of bucks between successive breeding seasons?
Male quality changed with age, inducing a change in quality-related parameters and thus, a modification of vocal cues to male individuality between years.
Same-year correct classification rates (36.09 ± 0.05%) were significantly higher than cross-year correct classification rates (21.62 ± 0.05%), indicating a between-years modification of vocal cues to male individuality (exact permutation test, P = 0.02).
A significant difference between same-year and cross-year correct classification rates would indicate a between-years modification of vocal cues to male individuality, according to the parameters measured in this study.
To investigate between-years modification of vocal cues to male individuality, we then calculated percentages of correct classification of PC scores (corresponding to groans) of one year by a DFA carried out on a previous year (cross-year correct classification rate; function predict in R v.2.9.0) [ 56].
Papers dealing with speech production in persons with hearing impairment, aphasia, dysarthria, voice disorders, and structural modifications of the vocal tract, as well as simulations of hearing loss and lexicons show how data from speech and hearing disorders may inform theory about normal processes.
A new model of songbird phonation is proposed, implying close coordination between the operation of the acoustic sources in the syrinx and dynamic modifications of the vocal tract.
