Multiple constraints on urban bird communication: both abiotic and biotic noise shape songs in cities

Abstract Ambient noise can cause birds to adjust their songs avoid masking. Most studies investigate responses a single source (e.g., low-frequency traffic noise, or high-frequency insect noise). Here, we investigated the effects of both anthropogenic and on vocalizations four common bird species in Hong Kong. Common Tailorbirds (Orthotomus sutorius) Eurasian Tree Sparrows (Passer montanus) sang at higher frequency urban areas compared peri-urban areas. Red-whiskered Bulbuls (Pycnonotus jocosus) shifted only first note song upwards. Swinhoe’s White-eye (Zosterops simplex) vocalization changes were correlated with level, but did not differ between populations. Insect caused Sparrow reduce maximum, peak frequency, overall bandwidth vocalizations. also led reduction maximum bulbuls. The presence affected sound Sparrows; areas, they no longer increased minimum when sounds present. These results highlight complexity soundscape high- ambient may make it difficult for signal masking while still maintaining fitness noisy cities.