Why pishing works: Titmouse (Paridae) scolds elicit a generalized response in bird communities

摘要

Pishing is a term used for the "psshh" noise made by bird watchers to elicit close approaches by small birds. Pishing usually attracts multiple species when used in Holarctic habitats, but it produces limited responses in other regions. We propose that responses to pishing occur most often because the sound mimics predator scold calls of species in family Paridae, whose members are resident primarily in the Holarctic. Using both field playback of recorded alarm calls and pishing and bioacoustic analysis of calls, we tested three hypotheses: (1) a generalized mobbing response to parid scold calls has evolved among forest birds in the Holarctic region; (2) pishing generates overt predator mobbing behaviour in diverse avian taxa; (3) pishing generates mobbing behaviour because of its acoustic similarity to parid scold calls. In playback trials in northern California, scolds of local and exotic parids and pishing elicited more vigorous mobbing responses than did the alarm calls of local non-parid species. Parid scolds shared two frequency metrics distinct from non-parid calls, and pishing shared one frequency metric with parid calls that was distinct from non-parid calls. We provide support for a generalized (mobbing) response elicited in Holarctic bird communities by parid scolds that could explain similar close-approach responses to pishing and provide evidence that scold call structural similarity with pishing may underlie the shared behavioural responses. This is the first test of mechanisms underlying pishing responses that also yields an explanation of the geographic variability in strength of response.