Comparison of acoustic recorders and field observers for monitoring tundra bird communities

Abstract

Acoustic recorders can be useful for studying bird populations but their efficiency and accuracy should be assessed in pertinent ecological settings before use. We investigated the utility of an acoustic recorder for monitoring abundance of tundra‐breeding birds relative to point‐count surveys in northwestern Alaska, USA, during 2014. Our objectives were to 1) compare numbers of birds and species detected by a field observer with those detected simultaneously by an acoustic recorder; 2) evaluate how detection probabilities for the observer and acoustic recorder varied with distance of birds from the survey point; and 3) evaluate whether avian guild‐specific detection rates differed between field observers and acoustic recorders relative to habitat. Compared with the observer, the acoustic recorder detected fewer species (βMethod = −0.39 ± 0.07) and fewer individuals (βMethod = −0.56 ± 0.05) in total and for 6 avian guilds. Discrepancies were attributed primarily to differences in effective area surveyed (91% missed by device were >100 m), but also to nonvocal birds being missed by the recorder (55% missed <100 m were silent). The observer missed a few individuals and one species detected by the device. Models indicated that relative abundance of various avian guilds was associated primarily with maximum shrub height and less so with shrub cover and visual obstruction. The absence of a significant interaction between survey method (observer vs. acoustic recorder) and any habitat characteristic suggests that traditional point counts and acoustic recorders would yield similar inferences about ecological relationships in tundra ecosystems. Pairing of the 2 methods could increase survey efficiency and allow for validation and archival of survey results. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

Comparing the sampling performance of sound recorders versus point counts in bird surveys: A meta‐analysis

“…However, there was no such effect in the study by Vold et al. () based on the number of detections in the different distance bins, although the visual‐only detections could have offset an avoidance effect. In other studies (Hutto & Stutzman, ), no clear avoidance effect could be seen in histograms of detection distances excluding visual‐only detections.…”

“…Previous comparisons have thus far failed to find systematic habitat related differences in counts between recorders and humans (Celis‐Murillo et al., ; Van Wilgenburg et al., ) despite there being known differences in sound attenuation (Yip et al., ). It is probable that aural detectability in point counts and sound recordings are similarly affected by habitat and thus introduce no bias in our comparisons owing to the nature of the paired comparisons (Van Wilgenburg et al., ; Vold et al., ). Moreover, our analyses correcting for detection ranges implicitly accounts for the habitat effect on sound detection range.…”

“…Sound recorders did not sample larger detection ranges than point counts, so when bird detection distances were available, the point count data were filtered to include only detections below a distance that corresponded to the sound recorders' detection range as estimated by the authors. In some cases, bird detection distances were available for sound recordings as well, which helped to truncate detection ranges of both survey methods to a more sensible threshold (Darras, Furnas, Fitriawan, Mulyani, & Tscharntke, ; Sedláček et al., ; Vold, Handel, & McNew, ; Wa Maina et al., ). This resulted in species richness values for identical or at least similar ranges (hereafter termed “identical”).…”

Autonomous sound recording outperforms human observation for sampling birds: a systematic map and user guide

“…Vold et al. () showed that even in tundra bird communities, visual obstruction was not associated with detected bird abundance. In more heterogeneous montane habitats, McGrann and Furnas () detected only 1% of birds just visually and in forest, Darras et al.…”

Estimating bird detection distances in sound recordings for standardizing detection ranges and distance sampling

“…It follows that any comparison of point counts vs. sound recordings with regard to variables like abundance or species richness is biased if the differing detection ranges are not taken into account (Darras et al., ; Yip, Bayne, Sólymos, Campbell, & Proppe, ), as these variables increase with the sampled area. Indeed, it has been suggested recently that the differing effective detection ranges may cause the discrepancy in richness values between point counts and sound recorders (Van Wilgenburg et al., ; Vold, Handel, & Mcnew, ). However, so far bird species richness values were used as measure to compare the sampling efficiency of point counts vs. autonomous sound recorders in several studies (Shonfield & Bayne, ).…”