A study by UC Santa Cruz's Forest Fear Lab found that alarm calls in the Peruvian Amazon rainforest are widely shared across species, creating a temporary communication network.
Researchers used trained raptors to trigger warning calls, then played recordings back to observe responses. The study, published in Current Biology, showed that small bird species under 100 grams were most likely to relay calls, and larger species such as capuchin and spider monkeys sometimes responded.
Two nunbird species were particularly active in propagating warnings.