An electronic system to collect distance‐sampling data during helicopter surveys of northern bobwhite

Abstract

Distance sampling during aerial surveys has been used extensively to estimate the density of many wildlife species. However, practical issues arise when using distance sampling during aerial surveys, such as obtaining accurate perpendicular distances. We assembled a computerized, electronic system to collect distance‐sampling data (e.g., transect length, detection location, and perpendicular distance) during aerial surveys. We tested the accuracy of the system in a controlled trial and a mock survey. We also evaluated the electronic system during field surveys of northern bobwhite (Colinus virginianus) conducted in the Rio Grande Plains and Rolling Plains ecoregions of Texas, USA, during December 2007–2008. For comparison, we evaluated the accuracy of visual estimation of distance during a mock survey. A strong linear relationship existed between estimated and actual distances for the controlled trial (r2 = 0.99) and mock survey (r2 = 0.98) using the electronic system. Perpendicular‐distance error (i.e., absolute difference between estimated distance and actual distance) for the electronic system was low during the controlled trial (1.4 ± 0.4 m; ${\bar {x}}$ ± SE) and mock survey (3.0 ± 0.5 m) but not during the visual estimation of distance (10 ± 1.5 m). Estimates of bobwhite density obtained using the electronic system exhibited reasonable precision for each ecoregion during both years (CV < 20%). Perpendicular‐distance error slightly increased with target distance (0.7‐m increase in error for every 10‐m increase in target distance). Overall, the electronic system appears to be a promising technique to estimate density of northern bobwhite and possibly other terrestrial species for which aerial‐based distance sampling is appropriate. © The Wildlife Society, 2012

Factors affecting trapping success of northern bobwhites in the rolling plains of Texas

“…Texas Parks and Wildlife Department's (TPWD 2012) annual roadside counts during this study were well below the longterm mean of 20.5 bobwhites/32-km route for the Rolling Plains. Declines in relative abundance at RPQRR were also observed based upon various ongoing indices (e.g., helicopter surveys; Schnupp et al 2013). Helicopter surveys were conducted annually during the first week of November.…”

Using mark–recapture distance sampling methods on line transect surveys

“…; Schnupp et al . ). Lines, or points, are laid down at random (or with some random component), and an observer travels along the lines, or stands at points, collecting information about the target species.…”

“…Plumptre 2000; Wegge & Storaas 2009;Heide-Jørgensen et al 2010), using a range of survey platforms, such as boats, planes, helicopters, cars and walking observers (e.g. Marini et al 2009;Schnupp et al 2013). Lines, or points, are laid down at random (or with some random component), and an observer travels along the lines, or stands at points, collecting information about the target species.…”

An evaluation of population indices for northern bobwhite

“…Helicopter surveys are used as both indices and abundance estimators for bobwhite (Shupe et al , Rusk et al , Schnupp et al ). Many managers conducting helicopter surveys do not collect distance data.…”

“…Methods for obtaining ‘absolute’ abundance estimates for bobwhite include mark–recapture (Petersen , Lincoln ) and distance sampling (Buckland et al ) using walking transects (Guthery , Rusk et al ) or helicopter transects (Rusk et al , DeMaso et al , Schnupp et al ). Intensive mark–recapture methods are considered, by some, as the standard for estimating abundance (Pierce et al ).…”