Song variation across space and time in Anna’s Hummingbird (Calypte anna)

Birds use song to communicate in multiple contexts, including territoriality and courtship. Of particular interest is the phenomenon of song sharing, in which direct neighbors’ songs are more similar to one another than those of non-direct neighbors. Song sharing has been studied extensively in oscine songbirds. However, despite the high diversity of hummingbird vocalizations, less attention has been given to this lineage. Anna’s Hummingbird (Calypte anna) has a spectrally complex, three-phrase multisyllabic song that varies on both macrogeographic and microgeographic scales. In this study we tested for song sharing between neighbors and for an effect of physical distance on song distance within a single population. In January and February of 2021, we audio recorded 29 Anna’s Hummingbirds in Golden Gate Park, San Francisco, CA. We characterized syllable types, and measured spectral and temporal features of songs in Raven Pro 1.6. We evaluated how Anna’s Hummingbird song form may change over time by comparing our results to those of a study conducted at the same site in 1999 and recordings from the 1980s. In our recordings from 2021, we identified 25 syllable types and eleven song types, and found evidence for both syllable and song type sharing between males with adjacent territories. We found high turnover of syllable types between the 1980’s and 2021, demonstrating the potential for rapid cultural evolution in hummingbird song.