The signal value of vocalisations revealing auditory threat assessment in meadow pipit males (Anthus pratensis)

Abstract

ABSTRACT If territorial males are able to assess the extent of threat posed by con- and heterospecific intruders in an area of sympatry, they could optimise the expression of territorial behaviour. I broadcast recorded vocalisation types of meadow and rock pipit males in the centre of territories to address the following questions: (1) do meadow pipit males respond to conspecific Soft calls, the (’contact’) call emitted by conspecific birds that do not represent a threat to territory or the resident male’s mate; (2) if so, how intensely do they respond to conspecific Soft calls compared with more provocative vocalisations emitted during territorial defence, including the Tsip call elicited by a watching male, or the species-specific part of song (Motif II) – associated with a serious territorial threat; (3) do they discriminate between the homologous Soft calls of meadow and rock pipits? Territorial males responded to conspecific Soft calls as often as to the other two vocalisation types broadcast in territories, but they did not approach the speaker as immediately or as often as to either Tsip or Motif II calls. The latter call elicits a more intense response compared with Tsip. Meadow pipit males discriminate conspecific from heterospecific Soft calls by showing enhanced response to conspecific relative to heterospecific Soft calls.