A small vocal repertoire during the breeding season expresses complex behavioral motivations and individual signature in the Common Coot

Background: Although acoustic communication plays an essential role in the
social interactions of Rallidae, our knowledge of how Rallidae encode
diverse types of information using simple vocalizations is limited. We
recorded and examined the vocalizations of a Common Coot (Fulica atra)
population during the breeding season to test the hypotheses that 1)
different call types can be emitted under different behavioral contexts,
and 2) variation in the vocal structure of a single call type may be
influenced both by behavioral motivations and individual signature. We
measured a total of 61 recordings of 30 adults while noting the behavioral
activities in which individuals were engaged. We compared several acoustic
parameters of the same call type emitted under different behavioral
activities to determine how frequency and temporal parameters changed
depending on behavioral motivations and individual differences. Results:
We found that adult Common Coots had a small vocal repertoire, including 4
types of call, composed of a single syllable that was used during 9 types
of behaviors. The 4 calls significantly differed in both frequency and
temporal parameters and can be clearly distinguished by discriminant
function analysis. Minimum frequency of fundamental frequency (F0min) and
duration of syllable (T) contributed the most to acoustic divergence
between calls. Call a was the most commonly used (in 8 of the 9 behaviors
detected), and maximum frequency of fundamental frequency (F0max) and
interval of syllables (TI) contributed the most to variation in call a.
Duration of syllable (T) in a single call a can vary with different
behavioral motivations after individual vocal signature being controlled.
Conclusions: These results demonstrate that several call types of a small
repertoire, and a single call with function-related changes in the
temporal parameter in Common Coots could potentially indicate various
behavioral motivations and individual signature. This study advances our
knowledge of how Rallidae use “simple” vocal systems to express diverse
motivations and provides new models for future studies on the role of
vocalization in avian communication and behavior.