Breeding barn swallows recognize householders from strangers.

The aim of this study was to investigate the ability of barn swallows (Hirundo rustica) to recognize humans. A field study was conducted in Caoyang Village, Zhanjiang City, Guangdong Province, South China. We assessed the responses of female barn swallows to the recognition of different types of human individuals by measuring their flight initiation distance (FID) when they incubated eggs in the nests. Our results demonstrated that barn swallows can identify the householder where their nest is located, displaying lower FID when the householder approaches, compared to an unfamiliar experimenter. Furthermore, there was no significant difference in FID between swallows reacting to householders who were rarely at home versus those who were frequently present, suggesting that barn swallows may possess the capability to recognize and retain memory of individual humans over time. Our findings provide evidence that barn swallows exhibit remarkable cognitive abilities. The long-standing symbiotic relationship between barn swallows and humans provides a unique model for studying the adaptation of species to environments with close human interactions. Research on their behavior and survival strategies can offer insights into the influence of symbiotic relationships on species adaptability and evolution.