Advanced Technologies for Acoustic Monitoring of Bird Populations

摘要

DoD lands are critically important to migratory bird species as breeding sites, wintering sites, and as migratory stopover sites. The Endangered Species Act (ESA) requires that US military installations monitor the status of federally listed threatened and endangered species (TES) on their grounds. The standard approach to monitoring populations of breeding songbirds relies on point counts in which a skilled observer notes the species, and in some cases the numbers, of all birds heard or seen at a sampling point during a short (typically 3 / 10 minute) count interval. Often the majority of individual bird detections in point counts are acoustic; many of the birds noted during a typical count are never seen. In suburban landscapes, closed- canopy deciduous habitats, and tropical forested habitats, acoustic detections can comprise 70 / 94% of all detections (Alldredge et al. 2006, and references therein). In monitoring some groups such as nocturnal birds (notably owls and nightjars) and some secretive marsh birds, virtually all detections are acoustic. In some of these species, monitoring efforts are further hampered by the birds, infrequent and unpredictable vocal activity, which may require impractically long observer times at each point in order to have reasonable confidence about the absence of a species at the site. Because acoustic detection plays such a prominent role in avian population monitoring, the use of automated acoustical recording instruments and signal detection and classification software has the potential to lead to improved monitoring of bird populations on DoD lands and elsewhere. Specifically, such techniques may enable more extensive sampling, improved estimates of the birds counted and missed, and improved estimates of the area surveyed.