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Effects of experimental playbacks on availability for detection during point counts
Citation:
Grinde, A., G. Niemi, AND M. Etterson. Effects of experimental playbacks on availability for detection during point counts. Journal of Field Ornithology. Wiley InterScience, Silver Spring, MD, 89(1):93-104, (2018). https://doi.org/10.1111/jofo.12242
Impact/Purpose:
This manuscript is intended for the general ornithological community. It describes the influence of heterospecific vocalizations on the detection probability of birds during point count surveys. It will be useful for understanding how different conditions influence count-based surveys of birds.
Description:
Point counts are the most commonly used technique for surveying passerines during the breeding season. Several methods for estimating probabilities of detection during point count surveys have been developed. These methods have primarily focused on accounting for the influence of environmental factors (e.g., weather, noise) on detectability however the probability that a bird is available for detection (e.g., sings or moves) during the point count has received considerably less attention. We used sequential point counts to determine the effect Black-capped Chickadee (Poecile atricapillus) mobbing playbacks and Red-tailed Hawk (Buteo jamaicensis) flight calls have on availability for detection (e.g., sings or moves) during a point count surveys. We conducted 180 point counts over a two year time period to evaluate the impact of playbacks on observed density, overall species richness, minute of first detection, and distance of first detection. We also used removal models to quantify the magnitude of changes in detectability and direction of response to playbacks for 10 focal species. Mobbing playbacks significantly increased observed density, decreased average distance of detection and time of first detection whereas predator flight call playbacks significantly decreased observed density and species richness, and increased mean time of first detection. Playback treatment was a covariate in all best performing models for the 10 species analyzed, but the magnitude and direction of response to playbacks were species specific. Other factors that influenced detectability were time of day, which increased detectability for three species and Julian date, which decreased detectability for two species. The importance of playback type in detectability models indicates that heterospecific calls can influence species availability for detection. We suggest that researchers using playback methods should seek to quantify species-specific responses in detection probability and consider how component detection probabilities could influence survey outcomes.
URLs/Downloads:
DOI: Effects of experimental playbacks on availability for detection during point counts