Multiple Community Informants Enhance Public Information About Predators Across a Latitudinal Gradient in Bird...

"Community informant" species serve as critical sources of information. However, interactions between multiple informant species in complex systems remain unclear, including whether they jointly contribute vocalizations and thus public information, eavesdrop on each other, or do not interact, and whether joint contributions provide benefits through complementary or supplementary mechanisms. We elicited mobbing calls using an owl model and alarm calls using a raptor model inside mixed-species flocks (MSFs) in a two-year survey on a 1650 km latitudinal gradient (18.7°N-33.7°N) in China, across which bird communities transition from babbler dominance in the south to tits in the north. We also constructed social networks to examine structural patterns along the gradient and assessed the influence of latitude on network metrics and the effect of group composition (Babbler-Tit, Babbler, Tit, None) on vocal responses. Social network metrics peaked in interaction strength (for mobs) and cohesion (for MSFs) at mid-latitudes. Alarm calls were brief and dominated by one babbler and two tit species, whereas mobbing calls were long-lasting and contributed by many species (averaging 4.2 per trial). In small mobbing assemblages (1-5 species), Babbler-Tit groups recruited up to 2.4 times more individuals and elicited 2.1 times more calls. Babbler-Tit MSFs also involved up to 1.6 times more vocal species and generated vocalizations with up to 12.2 times broader frequency ranges, which potentially could be detected by more species. Therefore, protecting community informants and complex systems is essential to maintain information networks that underpin ecosystem resilience.