What's the rumpus? Resident temperate forest birds approach an unfamiliar neotropical alarm call across three continents

Abstract

Alarm signals have evolved to communicate pertinent threats to conspecifics, but heterospecifics may also use alarm calls to obtain social information. In birds, mixed-species flocks are often structured around focal sentinel species, which produce reliable alarm calls that inform eavesdropping heterospecifics about predation risk. Prior research has shown that Neotropical species innately recognize the alarm calls of a Nearctic sentinel species, but it remains unclear how generalizable or consistent such innate signal recognition of alarm-calling species is. We tested for the responses to the alarm calls of a Neotropical sentinel forest bird species, the dusky-throated antshrike (Thamnomanes ardesiacus), by naive resident temperate forest birds across three continents during the winter season. At all three sites, we found that approaches to the Neotropical antshrike alarm calls were similarly frequent to the alarm calls of a local parid sentinel species (positive control), while approaches to the antshrike's songs and to non-threatening columbid calls (negative controls) occurred significantly less often. Although we only tested one sentinel species, our findings indicate that temperate forest birds can recognize and adaptively respond globally to a foreign and unfamiliar tropical alarm call, and suggest that some avian alarm calls transcend phylogenetic histories and individual ecological experiences.

Keywords: alarm call; avian alarm calls; avian mixed-species flocks; heterospecific eavesdropping; sentinel species‌; vocalization.

Figure 1.

Spectrograms of playbacks and world map of playback sites. (a) Alarm calls of sympatric tit species, serving as positive control. (b) The alarm call of the dusky-throated antshrike, a foreign sentinel species. (c) The loudsong of the dusky-throated antshrike. (d) The loudsong of a sympatric dove species, serving as negative control. (e) World map of three sites. Playbacks are marked with coloured dots for each site where they were played.

Figure 2.

Average approach of birds to various playbacks conducted at temperate sites in North America, Europe, and Asia. Playback type was a significant predictor of response, independent of geographical site.