A CASE OF POSSIBLE VOCAL CONVERGENCE BETWEEN FROGS AND A BIRD IN HIMALAYAN TORRENTS

Several species of frogs of the subgenus Paa of the genus Rana and the bird Phylloscopus magnirostris, which call in or near torrents in the Himalayas, shows striking similarities in their vocal signals: the calls are composed of short sequences of notes separated by periods of silence; the notes are pure, short, and have a narrow frequency band; within each sequence, the notes are rhythmically emitted. These characteristics may be adaptive, the convergence being caused by the selective pressure of the acoustic constraints of the biotope.