Breeding vocalizations of the piping plover (<i>Charadrius melodus</i>): structure, diversity, and repertoire organization

Abstract

We studied breeding vocalizations and the vocal repertoire of the endangered piping plover (Charadrius melodus Ord, 1824) to describe diversity of the species' non-learned vocalizations, provide a basis for comparative studies, and enable standardization of terminology and interpretation of vocal classes for management purposes. Adults have 14 call types and newly hatched chicks have three; these are underestimates of repertoire size because they represent breeding vocalizations only and are biased toward loud, easily recorded sounds. Vocalizations are structurally diverse: duration, ~10 ms to 1.5 s; peak frequency (adults), &lt;900 to &gt;3000 Hz; tonal to pulsed or noisy; narrow- to broad-band; and nonharmonic to harmonic. Vocalizations are higher in frequency in females than in males. High vocal diversity results from differential combination and sequencing of fairly simple acoustic attributes such as pulsing and frequency modulation, and from quantitative variation in such attributes. Homologies with other species of Charadriidae in acoustic traits of calls, call types, and organization (syntax) within calls and across call types are suggested. Acoustic characters at different organizational levels are highly conserved evolutionarily; hence, they seem to hold promise for phylogenetic analyses within the family.