Winter Macro- and Microhabitat Use of Winter Roost Sites in Central Missouri

Northern bobwhite (Colinus virginianus) managers and biologists have expressed concern regarding the apparent decline of northern bobwhite populations throughout the Unites States. The decline has been attributed to habitat loss; however, the decline may be the result of multiple factors. Several studies concluded that reproduction was not a limiting factor, and recommended that investigations of winter habitat use at the microhabitat level are needed. In our study, we used data from 166 roost sites obtained from 194 radiomarked bobwhites to analyze winter macrohabitat use and microhabitat characteristics of roosts selected by bobwhites in central Missouri. At the macrohabitat level, bobwhites showed a preference for early successional vegetation (ESV), native warm-season grass (NWSG), and old (idle) fields. Most roost locations (5l.2%) were in old fields, in ESV (23%), and NWSG (l7%). For all 3 habitat types (old fields, ESV, NWSG), litter at the roost site was higher (P \u3c 0.05) than the surrounding vegetation. In the 2 most preferred habitat types, visual obstruction reading (VOR) and maximum vegetation height were higher (P \u3c 0.05) than the surrounding vegetation. In NWSG and old fields, litter depth was significantly higher (P \u3c 0.05) than the surrounding vegetation. Habitat management of winter cover in central Missouri will benefit from the maintenance of dense ground litter (\u3e 65%), tall vegetation (91 cm), VOR (29 cm), and litter depth about 1.5 cm in ESV, NWSG, and old fields

Vegetation and Thermal Chracteristics of Bobwhite Nocturnal Roost Sites in Native Warm-Season Grass

Native warm-season grass (NWSG) has been widely promoted as wildlife habitat, but little empirical evidence is available to support its value for most wildlife species. One justification for a conversion to NWSG is the high thermal quality of cover resulting from the height and structure of the vegetation. Because vegetation cover is an important factor contributing to bobwhite winter survival, we predicted that they should select roost sites with superior thermal characteristics during winter when energy requirements for thermoregulation are greatest. In this 3-year study we used data derived from roost sites (n 166) obtained from radio-marked quail to compare the relative use of NWSG and 5 other habitat types, and the micro-habitat characteristics of winter roost and random sites on an area intensively managed for quail in Missouri. Of the 6 habitats used for roosting, most locations (51.2%) were in old-field habitats. NWSG ranked third with 17% of the locations. Our findings indicated that roost site selection may be influenced to a greater extent by the micro-habitat characteristics of a site rather than by habitat type. Two micro-habitat features that were of particular importance in habitats used most by quail were litter cover and canopy cover. These habitat features are valuable in reducing conductive and convective heat loss

Use of Weather Variables for Predicting Fall Covey Calling Rates of Northern Bobwhites

A newly developed technique for estimating fall northern bobwhite (Colinus virginianus) density is currently being employed in parts of the United States. One aspect of this technique involves predicting morning covey calling rates (i.e., the proportion of coveys that call on a given morning). We monitored 60 radiomarked coveys, a total of 229 covey observations, to determine whether or not each covey called. Calling rates were evaluated in relation to date, year, area, temperature, relative humidity, barometric pressure, barometric status, cloud coverage, and wind speed. We used logistic regression to test 9 a priori models as predictive models of bobwhite covey calling behavior. Models were compared using Akaike information criteria (AICc) values to determine the relative importance of 6 different variables (wind speed, date, temperature, cloud coverage, barometric pressure, and relative humidity). An exploratory analysis was then conducted to find the best predictive model using the best subsets model selection procedure. Standard errors of the coefficients in the best models were calculated using a traditional bootstrapping technique. We found an overall calling rate of 78%. Wind speed and date were the most influential of the 6 variables used in a priori model tests. Nine of the 19 exploratory models fit the data reasonably well. The best model included area and wind speed as independent variables, and was a better model than the best a priori model. There was a difference in calling rates between areas, and as a consequence, we recommend caution in application of our models to new areas

Winter Cover Height and Heat Loss: Is Taller Better? (Oral Abstract)

Previous studies have demonstrated that roost site selection affects energy requirements for thermoregulation in several avian species; however, the influence of microhabitat characteristics on heat loss has not been evaluated for northern bobwhites (Colinus virginianus). One frequently measured microhabitat feature that is commonly thought to influence the thermal characteristics of avian ground roost sites is cover height. We simultaneously measured thermoregulatory energy expenditure of bobwhites across a range of low ambient temperatures (-24 to 14 C) in 3 cover heights (0 cm, 46 cm, 124 cm) using 3 heated taxidermic mounts. Predicted metabolic rates (PMR) were derived on the basis of power consumption of the taxidermic mounts. Predicted metabolic rate for each vegetation height was linearly related to ambient temperature, and decreased significantly (P \u3c 0.05) as temperature increased. Contrary to our predictions, PMR did not differ (P = 0.769) among the 3 vegetation heights across a range of environmental conditions. These findings suggest that under the conditions occurring during our field measurements, thermoregulatory energy requirements of bobwhites are essentially independent of vegetation height at the roost, and primarily are a function of conductive rather than convective heat loss

Improving Quail Management Through Statistical Modelling (Poster Abstract)

Northern bobwhite (Colinus virginianus) populations have been declining since the 1960s. Anthropogenic influences, particularly farming, are suspected to be 1 of the most significant contributors to loss of landscape diversity and thus the present scarcity of bobwhites. Because of habitat degradation on private lands, management on public areas is critical to sustain populations. To understand the efficacy of management efforts, information relating survival and nest success to habitat characteristics within intensively managed areas is needed. Within Missouri, management is currently based upon data collected from poor habitat on private agricultural land in northeast Missouri. Population dynamics within agricultural habitat are not necessarily relevant to intensively managed areas. Our research was conducted on 3 conservation areas that focus on bobwhite management. This poster will present population data that will eventually be incorporated into a model identifying factors that affect bobwhite reproduction and survival. Data were derived from radiomarked birds that were located 6 days/week to document survival. We monitored incubating birds until nest termination to determine nest success. The probability of surviving to the end of the first field season (1 May–30 Sep 2000) was 0.021 (SE = 0.08, n = 95). At the end of the first field season, 6 birds survived, 55 died, 12 slipped the radio collar, and 22 were censored due to disappearance of the radio signal (unknown fate). Overall nest survival during the 22-day incubation period was 54.8%. Results of this research will provide managers insight into the effects of habitat manipulations on bobwhite populations