Long-term bioacoustic monitoring for gauging animal populations: An approach involving flight calls of night migrating songbirds

Abstract

At times during the course of a year, the airspace over most locations in North America contains flight calls of night migrating songbirds. The calls typically have an audio frequency between 2 and 10 kHz and are 0.03-0.4 s in duration. Documenting such calls in a consistent manner enables temporal and quantitative calling patterns to be determined. Theoretically, such acoustic data gathered over time could be used as an index to population change as well as for documenting shifting migration routes. This presentation will discuss the development of a multi-sensor system designed to synchronously sample nocturnal flight calls of migrating songbirds across eastern North America. We will review the decisions involved with the system design that minimize non-target aspects of the soundscape and that help standardize monitoring over time. We will then illustrate the monitoring power of this application with flight call data from ten fall migrations at one monitoring station and two fall migrations from a transect of ten monitoring stations across eastern North America.