Evaluation of a vacuum technique to estimate abundance of waste barley

Abstract

Reliable estimates of seasonal waste-grain abundance are needed for wildlife conservation and management because these resources influence carrying capacity, behavior, and movement of birds. We tested efficacy and precision of a vacuum-sampling device for collecting waste barley Hordeum vulgare at Manitoulin Island, Ontario, Canada, 2011 and 2012. We used a Stihl BG 65E blower-vac to sample barley following methodology developed to sample moist-soil seeds. We collected samples by vacuum sampling (n = 51) and hand-picking (n = 51) in three randomly selected cut barley fields to estimate the proportion collected by vacuum sampling. We also collected experimental samples (n = 72) to estimate percent recovery using predetermined densities of dyed barley. Because our results were more variable and our percent recovery was less than published values, we acquired the blower-vac unit (BG 85) used in the moist- soil seed study to test for an equipment effect by repeating our experiments in 2012. We tested for equipment effects on percent recovery using generalized linear mixed-effect models with our observational and experimental data sets while controlling for spatial autocorrelation. Our analysis suggested that equipment type did not account for differences in percent recovery. Hand-picking yielded more precise estimates of waste barley density ((formula presented) = 97.1%, SD =7.67%, n = 60) as compared with the blower-vacs under natural conditions (BG 65E: (formula presented) = 19.2%, SD = 96.0%, n = 27; BG 85: (formula presented) = 27.0%, SD = 40.37%, n = 24). Although the technique was not effective here for waste barley, we suggest that further research into small cereal grain applications is warranted.