Bioacoustic Monitoring Reveals Details of Tricolored Blackbird Breeding Phenology

Bioacoustic monitoring has been used to study behaviors of organisms from insects to whales. Studies using multiple vocalizations of a single species have the potential to determine detailed phenology, but to date they are rare. We tested whether bioacoustic monitoring of multiple gender- and age-specific vocalizations of the imperiled tricolored blackbird Agelaius tricolor could provide detailed information on reproductive phenology and breeding success. Using inexpensive cell phones and free software applications, we collected audio recordings of tricolored blackbird colonies during their breeding season. Adding solar panels enabled the stations to run autonomously, and use of cellular data enabled remote uploading of recordings. Analysis of the presence or absence of three vocalizations--male song, female song, and nestling call--provided a rich and detailed description of the breeding phenology including the dates for courtship; onset of nest building, incubation, and nestling hatching; and fledgling departure from nesting colonies. The resulting detail was more granular and accurate than comparable data from field monitoring, although field monitoring provides data such as abundance counts that bioacoustic monitoring does not. This information has a wide range of applications to research and conservation, from enabling more accurate abundance estimates, to assessing colony success or failure with fewer visits, to providing stronger guidance for when a colony must be protected from disruption.