Empirical measures of accuracy using small sensor arrays to localize animal vocalizations

Abstract Field studies using 3 and 4 sensor arrays were conducted to determine the accuracy and range of sound localizations. Under-ice and in-air trials examined the range/precision problems associated with deploying small arrays (77 m underwater, 14 m in air). The errors of the localized sound sources were determined within and outside of different array configurations in reverberant conditions. Using four receivers resulted in greater sound source localization accuracy than three. Variability of the sound source location errors within and outside of the arrays was high. The location accuracy and precision decreased when the sound source was located outside of the array. The measurement accuracy of the receiver positions was less important than the ability to determine very accurate time of arrival differences (TOAD) for each of the receiver pairs. The ability to cross correlate signals to determine TOADs appears to be the major difficulty. Also, there is a trade-off between the size of an array and the dynamic range of the call source levels that can be located. Only high amplitude calls can be localized using large (km wide) arrays. When using passive acoustic monitoring to locate fish and mammals, small hydrophone arrays will only provide accurate information when the sound source is within, or very close to the array

Winter Survival and Habitat Selection by Translocated Northern Bobwhite in the New Jersey Pine Barrens: Preliminary Results

Northern bobwhite (Colinus virginianus) populations have been experiencing precipitous range-wide declines for more than 50 years; some of the steepest declines occurring in the Mid-Atlantic states. These declines are largely attributed to habitat deterioration from urban sprawl, change in forest management, and intensive farming. This ongoing study aims to evaluate the efficacy of translocating wild bobwhites into the New Jersey Pine Barrens as a means to restore their historic populations. Translocation has proven relatively successful in augmenting bobwhite populations in other regions as well as restoring populations of gallinaceous species. This portion of the study aims to investigate what bobwhites require during winter months (October—March) in the Mid-Atlantic to survive until summer for reproduction. The study site, Pine Island Cranberry Company, is the largest privately owned tract of land (6,800 hectares) in New Jersey, with habitat comprised of pitch pine (Pinus rigida), shortleaf pine (Pinus echinata), scrub oak (Quercus ilicifolia), and early successional forbs and grasses. For three consecutive years (2015—2017) prior to breeding season, we will translocate 80 radio-collared bobwhites (40 male, 40 female) to Pine Island from wild populations in southwest Georgia. These bobwhites are radio-located 3—5 times per week throughout the year while this portion of the study focuses on the winter months. We are collecting microhabitat measurements (e.g., basal density, groundcover, understory, and canopy closure) from 30 random telemetry location points, per covey, per habitat type to characterize winter habitat use. Survival is estimated using staggered-entry Kaplan-Meier analyses and a Cox proportional hazard model in R to determine covariates of daily mortality. We are reporting on the first 2 years of results

Summer Survival of Translocated Northern Bobwhite in the New Jersey Pine Barrens: Preliminary Results

Northern bobwhite (Colinus virginianus) have declined precipitously since the 1960s, largely due to habitat deterioration and changes in land use; some of the highest declines have been observed in the Mid-Atlantic States. In other regions, attempts to augment bobwhite populations have been relatively successful using translocation. As part of a long-term restocking program, focal areas for translocation in the mid-Atlantic region were identified by biologists at a National Bobwhite Conservation Initiative (NBCI) workshop. The objective of this project is to evaluate translocation to restore bobwhite populations in the New Jersey Pine Barrens, a focal area designated with a high ranking for potential bobwhite recovery. The study site, Pine Island Cranberry Co., is the largest privately owned land tract (\u3e6,000 hectares) in New Jersey, with a mix of shortleaf pine (Pinus echinata), pitch pine (P. rigida), scrub oak (Quercus ilicifolia), and early successional forbes and grasses. For three consecutive years (2015—2017) prior to breeding season, we are translocating eighty radio-collared bobwhite (40 male, 40 female) from wild populations in southwest Georgia. These individuals are radio-located 3-5 times per week, year round. We are collecting microhabitat measurements (e.g., groundcover, understory, and canopy closure) and monitoring nests to characterize habitat use, nest site selection, and nest fate. Survival is estimated using staggered-entry Kaplan-Meier analyses and a Cox proportional hazard model in R to determine covariates of daily mortality. Six of 14 nests were successful in summer 2015 (66 known hatches), and 0 of 12 nests were successful in summer 2016. Snake depredation was the cause of 41.7% of failed nests in 2016. Preliminary analyses produce a five-month adult survival rate of 0.455 (SE = 0.138) for summer 2015 and 0.270 (SE = 0.0516) for 2016. Our planned third summer (2017) of data collection will increase our understanding of these disparate survival estimates

Highly Variable Autumn Calling Rates of Northern Bobwhite Following Translocation

Fall covey counts are a popular index for monitoring population trends of northern bobwhite (Colinus virginianus; hereafter, bobwhite), but their utility is tenuous under different scenarios. Detecting an individual covey is the product of the probability that the covey’s activity center is located within the sampling frame, the probability the covey is located within the sampling frame during the sampling periods, the probability of the covey vocalizing, and the probability an observer will detect a calling covey. Researchers attempt to maximize detection or account for these potential sources of error using standardized protocol of limiting counts to certain weather conditions, replication, and distance sampling. Variation in calling rates across a range of bobwhite densities could lead to tenuous inference of population abundance from fall covey counts, particularly at low densities. Our objectives were to assess fall calling rates at 2 sites with low bobwhite density during population restoration. Our study sites were located in Erath County, Texas, USA and Leon County, Florida, USA and received translocated bobwhite during 2019 and 2020. We hypothesized calling rates would be influenced by the number of adjacent coveys that called, and thus, would be low for our sites. Although we did not estimate bobwhite density on our study sites, we surmised that their respective populations were /3 ha. Calling rate at the Erath County site was 0 in 2019 (n = 10 counts) and increased to 0.79 (standard error [SE] = 0.07, n = 34 counts) in 2020. Calling rate was assessed only in 2020 at the Leon County site and averaged 0.13 (SE = 0.07, n = 23 counts). Detection rate at count stations was 0 in 2019 and 0.78 (SE = 0.08, n = 27 calling coveys) in 2020 at the Erath County site. In 2020, detection rate at count stations was 0 (n = 3 calling coveys) at the Leon County site. We documented high annual variation in calling rates among low-abundance sites, suggesting researchers should seek to empirically estimate this parameter rather than applying arbitrary correction factors based on previous literature. Low and variable calling rates limit detection and can bias inference

Effect of Food Distribution on Northern Bobwhite Resource Selection

Supplemental feeding is a common management tactic used to increase survival and reproduction of northern bobwhite (Colinus virginianus; hereafter, bobwhite). Different supplemental feeding methods alter the distribution of resources across a landscape in unique ways and may influence the space use and resource selection of target species differently. Predators may concentrate their movements near fed sites, and different distributions of supplemental feed may encourage bobwhite to concentrate their movements closer to feed than other areas, thereby altering the potential for predator-prey interactions near feed. We used radio-tracked locations and movements in areas with stationary feeders (“feeder fed”) and nonsupplementally fed (“unfed”; study 1, year 1) or nonstationary “broadcast fed” (study 2, year 2) areas to compare resource selection within a Bayesian framework. Second- and third-order resource selection functions indicated bobwhite were more likely to occur in proximity to feeders and feedlines when available, but bobwhite resource selection was more strongly affected by feeders. These results demonstrate that different distributions of food resources can affect prey resource selection, potentially altering the probability of overlap between nontarget predator and target prey species. Managers of bobwhite populations should broadcast feed instead of using feeders to avoid concentrations of bobwhites, which may lead to reduced survival

The Sexual Proclivities of Northern Bobwhites

Mating systems and mating behavior are historically viewed as static characteristics of populations. ‘Monogamy’, ‘polygamy’, ‘multiple clutch polygamy’, ‘polyandry’, etc. imply most individuals express similar social and genetic mating patterns and characterize the behavior of most or all individuals in a given population. Mating systems of different populations of northern bobwhites (Colinus virginianus) have been described as monogamous, polygamous, multi-clutch polygamous, ambisexually polygamous, and polyandrous in contrast to the expectation that behavior, at the species level, fits defined categories. Prior studies of bobwhite breeding behavior, to arrive at these classifications, were based on observations of social interactions and did not incorporate genetic outcomes. Thus, it is challenging to discern whether social behaviors predict genetic outcomes and whether bobwhite mating behavior varies among populations or if behavior is flexible within populations. We used 3 years of field observations and variation at 14 microsatellite loci of 601 adult and 841 neonatal bobwhites to estimate rates of extra-pair paternity in bobwhite broods, evaluate the utility of social behavior as an indicator of genetic outcomes, and evaluate the fit of bobwhite social and genetic behavior to classic mating system theories. Extra-pair paternity occurred in \u3e50% of bobwhite broods, whereas extra-pair matings resulted in few (x¯= 1.1) extra-pair offspring per nest. Social interactions between female and male bobwhites generally predicted the father of most offspring in a brood, but social interactions did not predict extra-pair matings better than chance. The mating behavior of individual females changed within and between breeding seasons, suggesting individual reproductive decisions of females were flexible. The mating ‘system’ of bobwhites meets neither the predictions nor the assumptions of classic mating theories