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Northern bobwhite (Colinus virginianus) populations have been declining in Texas during the last 2 decades. This decline also is occurring in areas with apparently ample habitat such as the Rolling Plains of Texas, USA. The goal of our study was to examine the efficacy of translocating wild-trapped bobwhites into recently depopulated areas in the eastern Rolling Plains as a method of restoring population size. Our objectives were to document survival (spring-summer and annual), reproductive efforts, and site fidelity of translocated bobwhites and compare relative abundance of bobwhites between release and control sites to evaluate the efficacy of translocation. We translocated 409 wild bobwhites (n ¼ 186 radio-marked F) to 2 sites in Shackelford and Stephens counties, Texas, during March 2013 and 2014. Spring-summer (Mar-Sep) survival ranged between 0.32 and 0.38 (n ¼ 186 bobwhites), and annual survival ranged between 0.19 and 0.23 (n ¼ 186 bobwhites) during 2013-2015. Seventy-four percent of translocated females that entered the nesting season (i.e., May 1; n ¼ 112 bobwhites) produced a nest, resulting in 125 nests with an apparent nest success of 46.1% and a nesting rate of 1.1 AE 0.1 (SE) nests/female. Site fidelity post-translocation was moderate to high; 67.7% (n ¼ 44 bobwhites) and 85.1% (n ¼ 40 bobwhites) of translocated bobwhites did not disperse >2 km from their release point during the summers of 2013 and 2014, respectively. Despite this strong demographic performance, relative abundance of bobwhites did not differ between the release and control sites after 2 years as indexed by covey-call counts (2.7 AE 0.6 vs. 3.0 AE 1.2 coveys/point, respectively; P ¼ 0.71) and helicopter surveys (0.9 AE 0.2 vs. 0.7 AE 0.2 bobwhites/km, respectively; P ¼ 0.64). Thus, translocation of bobwhites failed to increase the bobwhite population beyond that of the control during this study. Future translocation research should aim to increase translocation success by investigating methods for increasing survival during the 1-month period following translocation (e.g., soft-release, vitamin E and selenium injections) and for improving site fidelity using conspecific attraction. Future research should incorporate genetic measures to assess genetic contribution of translocated individuals to improve evaluation of translocation success. Ó 2017 The Wildlife Society.
Understanding thermal ecology of endotherms is becoming increasingly important with predicted increases in temperature associated with climate change. Patterns of resource selection may depend in part on temperature thresholds outside which animals avoid warmer or cooler temperatures. During summer, northern bobwhites (Colinus virginianus; hereafter bobwhite) in semiarid areas often exist at the limits of their thermal tolerance. We sought to determine (1) selection bounds for black globe and ground surface temperatures, (2) whether ground surface temperature is a better predictor of the thermal environment used by bobwhites than black globe temperature, and (3) how time of the day influences thermal resource use. We radio‐marked 40 bobwhites and located them two to three times a week from April to September in 2014–2016. At each location, we measured ground surface and black globe temperatures at the bird location and at a location 20 m away in a random direction. We calculated continuous selection functions to estimate bounds of thermal characteristics suitable for bobwhites. We used generalized linear models to determine times of day bobwhites select cooler microclimates. Finally, we used case‐controlled logistic regression models to generate thermal resource selection functions. We compared models that included ground surface temperature, black globe temperature, and an index created from both variables with principal component analysis and selected the best model based on Akaike's information criterion adjusted for sample size (AICc) and log‐evidence ratios. Upper and lower selection bounds for black globe temperature and ground surface temperature were 24.5–42.5°C and 23.0–39.5°C, respectively. A principal component of black globe combined with ground surface temperature was a better predictor of bobwhite resource selection than either black globe temperature or ground surface temperature alone. In early afternoon (13:01–17:30 hours) during August, bobwhite locations had 13°C cooler black globe temperatures and 18°C cooler ground surface temperatures than random locations. Availability of thermally usable coverts (woody plant thickets) may be a limiting factor for bobwhites in the study area based on the findings that mean ground surface and black globe temperatures at used locations were close to the upper bounds for use in late summer during the middle of the day.
Introduction: Tanglehead is a grass native to southwestern US rangelands; however, its prevalence as a native invasive on South Texas rangelands has increased rapidly during the last decade. Large areas of monotypic stands have emerged in Jim Hogg, Duval, Brooks, and Kleberg counties. The aim of this research is to understand the spatial and temporal dynamics of these invasions as a model for the assessment of native invasive species. Our specific objectives were to (1) evaluate the feasibility of classifying tanglehead using 1-m resolution imagery data, (2) assess the spatial and temporal distribution of tanglehead in relation to soil type and distance from roads, and (3) quantify the temporal and spatial distribution of tanglehead on our study sites. We combined remote sensing approaches with landscape metrics to quantify the spatial and temporal distribution of tanglehead in five locations across our study area. We calculated the normalized difference vegetation index and combined it with the original aerial imagery to conduct an unsupervised classification with the following land cover classes: woody vegetation, tanglehead, non-tanglehead herbaceous, and bare ground. Soil type and the distance from roads were assessed to determine the relationship between these factors and tanglehead spatial distribution. Results: We were able to successfully map tanglehead using the 1-m imagery. Our image classification approach resulted in accuracies greater than 85% for all sites. Tanglehead occurred in sandy, loamy sand, and sandy loam soils. Over 70% of tanglehead cover occurred within the first 150 m from the edge of roads. This cover increased from 7.1% (SE = 1.1%) in 2008 to 17.8% (SE = 5.4%) in 2014. Once established, small patches of tanglehead began aggregating or coalescing with existing stands, thereby creating larger patches over larger areas. Conclusions: Our study has shown the value of analyzing spatiotemporal dynamics of tanglehead with remote sensing techniques and landscape metrics to improve our understanding of establishment and dispersal processes of a native invasive. This study provides useful information to improve rangeland management decisions as well as assessing native invasive dynamics with potential applications for assessing its effects on wildlife habitat, livestock operations, and habitat restoration strategies.
Diet selection theory predicts that selective foraging by white-tailed deer (Odocoileus virginianus) may reduce palatable and nutritious plants when high-quality food resources are available or deer densities are high. Our objectives were to determine if providing a high-quality food resource ad libitum and increasing deer densities 1) reduced standing crop and nutritional quality of forbs and 2) altered standing crop and nutritional quality of grasses and shrubs. We used 6 81-ha controlled-density enclosures on each of 2 study sites in southern Texas with deer densities considered low (12 deer/km 2 ), medium (31 deer/km 2 ), and high (50 deer/km 2 ) relative to the range of population estimates for white-tailed deer in the Rio Grande Plains of Texas. For each pair of enclosures with the same deer density at each study site, we provided whitetailed deer in 1 enclosure high-quality pelletized feed ad libitum and did not provide feed (control) in the other enclosure. During spring and summer 2004-2012, we estimated standing crop of forage in 40 0.25-m 2  1.5-m volumetric plots/enclosure and we harvested 20 randomly selected plots/enclosure, which we dried to convert wet mass estimates to dry mass. Availability of high-quality pelletized food and deer density did not affect (P ! 0.392) forb standing crop during spring and summer. Forb, browse, and grass standing crop and nutritional quality varied (P < 0.001) with precipitation among years. Enclosures with low deer densities had lower forb crude protein than those with higher densities (P < 0.034) during summer in drought years (2006, 2009, and 2011). Enclosures with high-quality pelletized food tended to have lower browse crude protein than controls (sampling date  feeding treatment interaction, P ¼ 0.051) in spring during 2006 and 2007. Variable and limited rainfall had a more pronounced effect on variation in vegetation standing crop than white-tailed deer foraging regardless of food resource availability or deer density. Vegetation responses were more complex than can be predicted by traditional theory on diet selection in part because of the pronounced effect of variation in rainfall on vegetation standing crop. Ó 2015 The Wildlife Society.
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