AUTHORS: Haley Holiman, Southern Illinois University; Brent. S. Pease, Southern Illinois University
ABSTRACT: Recently, the interest in and use of passive acoustic monitoring (PAM) to assess animal populations has continued to grow in popularity. Data collected from PAM has produced reliable estimates of species occurrence but estimating density remains challenging. For example, accurately estimating distance to individuals, double-counting, and isolating focal species’ calls in diverse areas can hinder density estimation. Eastern whip-poor-wills (Antrostromus vociferus) are nocturnal aerial insectivores with distinct vocalizations and may be ideal candidates for density estimation using PAM, however, little guidance exists for sampling protocols and analytical frameworks. Here we present results from a density estimation pilot study in Morgan-Monroe and Yellowwood State Forests, Indiana, USA that paired PAM with point count surveys. From May – July 2022, we deployed acoustic recording units and conducted nocturnal point count surveys for whip-poor-wills across different forest management plots. Our objectives were to evaluate four analytical frameworks for estimating density of whip-poor-wills: distance sampling and binomial n-mixture models using time-to-detection from PAM and point counts. Preliminary results suggest that ARUs may provide comparable estimates of nightjar density to traditional point counts, and density estimates appear consistent across varying silvicultural management techniques. Future work to be conducted in 2025-2026 includes expanding the study area, optimizing ARU sampling protocols for density estimation of nightjars, and relating forest management practices to nightjar abundance.
