Observer effects and avian-call-count survey quality: Rare-species biases and overconfidence

Abstract

ABSTRACT. Wildlife monitoring surveys are prone to nondetection errors and false positives. To determine factors that affect the incidence of these errors, we built an Internet-based survey that simulated avian point counts, and measured error rates among volunteer observers. Using similar-sounding vocalizations from paired rare and common bird species, we measured the effects of species rarity and observer skill, and the influence of a reward system that explicitly encouraged the detection of rare species. Higher self-reported skill levels and common species independently predicted fewer nondetections (probability range: 0.11 [experts, common species] to 0.54 [moderates, rare species]). Overall proportions of detections that were false positives increased significantly as skill level declined (range: 0.06 [experts, common species] to 0.22 [moderates, rare species]). Moderately skilled observers were significantly more likely to report false-positive records of common species than of rare species, whereas...