Habitat Value of Intensively Established Pine Plantations for Northern Bobwhite

ABSTRACT Declines in northern bobwhite (Colinus virginianus; bobwhite) populations in the southeastern United States may be partially attributable to loss of early successional plant cover associated with greater use of herbicides in forest management. We tested effects of 5 levels of operational plantation establishment intensity on vegetation communities and structure important for bobwhite in 1–5-year-old loblolly pine (Pinus taeda) plantations (n = 4) in the Outer Coastal Plain Mixed Forest of Mississippi. We compared results with values reported in the literature to calculate usable space for winter food, loafing, nesting, and brood-rearing at 2 levels of spatial resolution. Treatments (k = 5) reflected a range of management intensities and were combinations of mechanical site preparation, chemical site preparation (CSP), and herbaceous weed control (HWC). Coverage of winter food plants in the least intensive treatment was more than double that in the most intensive; however, differences in usable space of winter food cover were negligible due to improved accessibility in more intensive treatments. Although CSP reduced coverage of nonpine woody plants across all years, loafing cover reached adequate levels by year 3 in all treatments. Usable nesting cover was <4% across all years and treatments and was nearly eliminated by the reduction in herbaceous cover and visual screening cover following broadcast HWC. Optimal brood-rearing habitat was virtually absent in all treatments and years due to the lack of conjoint occurrence of bare ground and forb canopy. Although bobwhite habitat may have been promoted by formerly widespread plantation establishment methods that involved wide-scale soil disturbance, those established using newer methods with less soil disturbance are likely inadequate for most bobwhite habitat requirements. Efforts to provide bobwhite habitat in plantation-dominated landscapes may have to rely on management of thinned mid-rotation stands and permanent landscape features such as rights-of-way. The value of young plantations for bobwhite may be increased by reducing management intensity or increasing spacing between planting rows, thus increasing time before crown closure and providing opportunity for understory manipulations.     

Management Implications of Cover Selection Data: Northern Bobwhite Example

Abstract: We derived a method of estimating the direction and magnitude of cover changes for potentially maximizing wildlife abundance on an area. We illustrate the method with data on cover selection by northern bobwhites (Colinus virginianus) collected in the Texas Panhandle from 2000 to 2003. We used radiotelemetry to determine use of cover associations, Geographic Information System analysis to determine their availability, and logic related to use-availability analysis to collapse 95% kernel home ranges to usable space. Bobwhites selected mixed-shrub cover consisting of sand plum (Prunus angustifolia) and fragrant sumac (Rhus aromatica), and they avoided or neutrally used 8 other cover associations. However, grass upland and sand sagebrush (Artemisia filifolia) associations occurred in ≥86% of home ranges (n = 96 bobwhites with ≥30 radiolocations). Usable space averaged 54.2% ± 1.72 SE of kernel home ranges. The data indicated that adding about 226 ha of mixed-shrub cover or a structural homologue while simultaneously reducing the quantity of most other cover associations would maximize bobwhite abundance. An area with 30–60% mixed-shrub cover, with the balance in grass upland and sand sagebrush, and with cover dispersed such that no point was >30 m from mixed-shrub cover was hypothetically optimal for bobwhites in our region. Within certain constraints (e.g., financial, social, edaphic), managers can apply this method by manipulating cover types through relevant management practices (e.g., planting, prescribed burning, mechanical removal of vegetation). This method, with minor modification, could also be used to decrease usable space on an area, and thus decrease wildlife densities, should that be the manager's objective.     

Habitat Quality Following Mid-Rotation Treatment in Conservation Reserve Program Pines

ABSTRACT Evaluation of habitat management practices at mid-rotation is needed for pine (Pinus spp.) plantations enrolled in cost-share programs. Plantations established in abandoned agricultural fields may have different understory plant communities than those with a long history of forest cover. Mid-rotation pine plantations often have a hardwood midstory that limits development of early succession habitat components important to white-tailed deer (Odocoileus virginianus; deer) and northern bobwhite (Colinus virginianus; bobwhite). We treated with imazapyr herbicide and prescribed burning (HB) 11 thinned, 13–22-year-old pine plantations in the Upper East Gulf Coastal Plain of Mississippi, USA, enrolled in cost-share programs, and we sampled plant community response during the summers of 2003 and 2004, years 1 and 2 posttreatment. The HB treatment created a more open structure with greater coverage of debris and herbaceous plants than in controls. Increased forb coverage in HB plots yielded a more seasonally diverse foraging base for deer. Horizontal screening cover developed slowly in HB plots and was more abundant in control plots. Autumn and winter food-plant coverage for bobwhite was provided by either treatment, but accessibility was improved in HB plots relative to controls. Bobwhite nesting cover was improved by HB relative to controls but was still of marginal quality. Brood-rearing habitat was precluded in both treatments due to lack of bare ground. Our results indicate that imazapyr followed by prescribed fire is a beneficial tool for creating early succession habitat for deer and bobwhite in mid-rotation pine plantations with a history of agricultural use. Continued management with periodic prescribed fire and overstory thinning should be instituted to maintain and perhaps improve these conditions.     

Economics of Northern Bobwhite and Timber Management in the Southeastern United States

ABSTRACT Populations of northern bobwhite (Colinus virginianus) have declined significantly over the past 50 years, and the primary factor contributing to this decline has been the loss of habitat. Forest landowners who are concerned with providing bobwhite habitat as well as generating revenue from timber should balance the silvicultural requirements of timber production with the biological needs of the bobwhite. The goal of this study was to determine the economic tradeoffs between bobwhite and timber management and how to minimize loss or maximize profit when managing for bobwhite and timber simultaneously. I performed discounted cash flow analyses, calculated land expectation value, and determined the financially optimal rotation age and optimal timing and intensity of thinnings for loblolly pine (Pinus taeda) plantations under specific management objectives. My results show that the annual per-hectare economic gains of managing for both bobwhite and timber ranged from US$19.27 to $41.37 on site index 50 land, and ranged from $32.63 to $50.02 on site index 90 land. My analysis indicates that bobwhite management provides an investment opportunity to landowners whose low-productivity sites would be unprofitable if timber is the only product. My study provides an example of integrating multiple uses of goods and services in a way that maximizes economic returns and aids land managers in producing better habitat for bobwhite.     

Effects of Understory Vegetation Management on Brood Habitat for Northern Bobwhites

Abstract: Northern bobwhite (Colinus virginianus) populations have experienced severe declines for several decades, and declines have been particularly precipitous in the southern United States. These declines are partially attributable to large-scale conversions of potential habitat to short-rotation pine (Pinus spp.) forests managed for wood fiber production and fire exclusion in pine-dominated landscapes. We used standard arthropod sampling techniques, human-imprinted bobwhite chicks, and vegetation response to evaluate effects of different understory vegetation management practices on brood habitat quality within a commercially managed pine forest in Louisiana, USA, during 2002–2005. Specifically, we evaluated effects of mowing, prescribed fire during the growing season, prescribed fire in combination with imazapyr application, and no vegetation management on arthropod abundance and diversity, vegetation response, and the probability of bobwhite chicks successfully capturing an arthropod. Bobwhite chicks were more successful at capturing arthropods, and arthropod abundance and diversity were greatest, in plant communities managed using prescribed fire and imazapyr. Forest stands managed using a combination of fire and imazapyr were managed primarily to benefit the federally endangered red-cockaded woodpecker (Picoides borealis; RCW). Our findings suggest that management directed toward improving forest condition for RCWs improves habitat quality for brooding bobwhites. However, bobwhite chicks in our study area were less successful at capturing arthropods than were chicks in other studies in the southeastern United States. Brood-rearing habitat in pine forests similar to those we studied may be of generally poor quality, and could be related to precipitous declines of bobwhites in the West Gulf Coastal Plain. Managers should recognize that creating high-quality brood habitat in forests similar to those we studied will require more intensive management of understory vegetation than we studied.     

Northern Bobwhites and Postfire Succession

ABSTRACT Our study evaluated the effects of prescribed fire on northern bobwhites (Colinus virginianus) occupying native rangelands in Rolling Plains of Texas, USA, during 2002 and 2003. Prescribed fires were conducted during February of 1996, 1998, and 2000; pastures with no recent treatment history served as controls. We quantified bobwhite densities from line transects using distance sampling. We used a repeated-measures analysis of variance to test for treatment-year differences in bobwhite densities. We measured postfire herbaceous and woody vegetation attributes and evaluated vegetation relationships to bobwhite density using simple linear regression. We found significant between-year differences in fall bobwhite densities (F = 13.05, df = 3, P = 0.036) but no differences among treatments or controls. Fall bobwhite densities were inversely related to visual obstruction (r² = 0.179, df = 15, P = 0.058) and positively associated with increasing heterogeneity of grass cover (r² = 0.416, df = 15, P = 0.004). Our results suggest prescribed fire at large spatial scales may be a neutral practice for managing bobwhite habitat on semiarid rangelands.     

Northern bobwhite breeding season habitat selection in fire-maintained pine woodland

Despite the acknowledged importance of prescribed fire in creating northern bobwhite (Colinus virginianus) breeding cover, little research has investigated bobwhite breeding season habitat selection relative to time since fire. In 2016 and 2017, we monitored radio-tagged bobwhite on a 17,000-ha portion of a military installation managed with frequent (every ~3 years) prescribed fires, applied during the growing and dormant seasons. We monitored bobwhite to determine which vegetation characteristics associated with prescribed burning were important to bobwhite breeding season habitat selection at the microsite (i.e., telemetry location compared to nearby random location) and the macrosite scale (i.e., the burn-unit containing the location compared to study area availability). During 2 breeding seasons, we collected 2,315 bobwhite locations and compared percent cover of vegetation, days since burn, basal area, and distance to key landscape features (e.g., stream, wildlife opening) at a subset of microsite locations (301 locations during 2016 and 890 locations during 2017) to paired random locations. At the microsite scale, bobwhite selected lower basal area of hardwoods, greater woody understory cover, greater other (not wiregrass [Aristida stricta]) grass cover, and greater forb cover than at random points. At the macrosite scale, bobwhite selected units with <4.6 m²/ha basal area (combined hardwoods and pines) in 2016 and units with <9.2 m²/ha basal area in 2017. At the macrosite scale, bobwhite selected for areas burned in the dormant season of the same year, avoided areas burned in the growing season of the same year, and used other times since last burn categories proportionate to their availability. The selection for a low basal area at both scales indicates prescribed fire effects would be limited by shading from dense overstory, and the shrubs, grasses, and forbs that provide essential cover for bobwhite during the breeding season will not develop. In lower productivity soil regions similar to our study area, we advise that thinning operations set target basal areas below 10 m²/ha to create and maintain breeding season habitat for northern bobwhite. © 2019 The Wildlife Society     

Seed Bank Viability in Disturbed Longleaf Pine Sites

Some of the most species‐rich areas and highest concentrations of threatened and endangered species in the southeastern United States are found in wet savanna and flatwood longleaf pine (Pinus palustris Mill.) communities. Where intensive forestry practices have eliminated much of the natural understory of the longleaf ecosystem, the potential for reestablishment through a seed bank may present a valuable restoration opportunity. Longleaf pine sites converted to loblolly pine plantations and non‐disturbed longleaf sites on the Coastal Plain of North Carolina were examined for seed bank presence and diversity. Conducting vegetation surveys and examining the seed bank using the seedling emergence technique allowed for verification of the seed bank presence, as well as evaluation of the quality of the seed bank on disturbed longleaf pine sites. Forty‐three species and over 1,000 individuals germinated, and the seed banks of both the disturbed and non‐disturbed stand types contained species not noted in the vegetation survey. Although many of these species were considered weedy and typical of disturbance, numerous taxa were indicative of stable longleaf pine communities. This study confirms both the presence and quality of seed banks in highly disturbed former longleaf pine sites, suggesting that the seed bank may be an important tool in restoration efforts.     

Habitat-Suitability Bounds for Nesting Cover of Northern Bobwhites on Semiarid Rangelands

ABSTRACT Northern bobwhite (Colinus virginianus) is a species for which extensive knowledge exists regarding its ecology, life history, and habitat. Although the qualitative aspects of bobwhite habitat have been described and known for many decades, researchers have neglected to characterize bobwhite habitat quantitatively (i.e., habitat selection). Thus, biologists have been capable of identifying components that compose bobwhite habitat but have only been able to speculate on how much of each component was necessary. We documented selection-avoidance behavior of nesting bobwhites in Brooks County, Texas, USA, during May-August, 2004–2005. We measured 5 vegetation features (i.e., nesting-substrate ht and width, suitable nest clump density, herbaceous canopy coverage, and radius of complete visual obstruction) at nest sites (n = 105) and at random points (n = 204). We used continuous selection functions to assess habitat use and identify bounds of suitability. Selection domains for nesting-substrate height and radius of complete visual obstruction were 16.9–31.2 cm and 1.05-4.35 m, respectively. Across all measurements, bobwhites selected for nest sites with a nesting-substrate width ≥22.4 cm, suitable nest-clump density ≥730 nest clumps/ha, and herbaceous canopy coverage ≥36.7%. This knowledge will provide an important foundation for managers to evaluate current nesting conditions on semiarid rangelands and provide a basis for habitat management aimed at creating suitable nesting habitat for bobwhites.     

Effects of Tissue Collection Methods on Morphometrics and Survival of Captive Neonatal Northern Bobwhite

ABSTRACT We assessed effects of tissue collection methods (i.e., patagial microbiopsy and down feathers) and chick age at sampling on morphometrics and 21-day survival of 600 captive neonatal northern bobwhite (Colinus virginianus). We observed minimal effects on morphometrics and no difference in survival among patagial microbiopsy (x̄ = 0.96 ± 0.03), down feathers (x̄ = 0.92 ± 0.04), and control (x̄ = 0.86 ± 0.05) methods. DNA analysis from patagial microbiopsy, down feather, and egg tooth samples showed greater concentrations of DNA from patagial microbiopsy (x̄ = 10.28 ± 1.74 μg/ml) than either down feather (x̄ = 4.10 ± 1.74 μg/ml) or egg teeth (x̄ = 2.35 ± 1.74 μg/ml).     

Effects of Chronic Human Activities on Invasion of Longleaf Pine Forests by Sand Pine

Chronic human activities may result in new and permanent successional trajectories in certain ecosystems. The invasion of longleaf pine ecosystems by sand pine in the Florida Panhandle is one such change in the landscape. This study examined the spatial pattern of sand pine expansion and explored the natural and anthropogenic disturbances that fostered this invasion. Aerial photographs (1949, 1994) and Geographic Information Systems analyses confirmed sand pine expansion at Eglin Air Force Base. In 1949, there were 8,982 ha of sand pine in the southern portion of the study area near riparian and coastal lowland forests. By 1994, sand pine had expanded further upland and inland, for a total of 17,147 ha in the study area. Sand pine age data showed that this expansion had started by 1920 but increased rapidly in the 1940s. Historical accounts and structural data from stands suggest that land-use activities associated with the extraction of turpentine promoted the invasion by sand pine. Fires were suppressed in longleaf pine forests to protect turpentine trees, resulting in increased vegetation cover and decreased regeneration of longleaf pine. In addition, stands were typically harvested after turpentining, and there was little or no advanced regeneration of longleaf pine. Sand pine age histograms showed that the onset of high establishment rates (1940s) coincided with changes in land ownership and widespread fire suppression. Sand pine is likely to persist in these ecosystems due to its abundant regeneration. Received 17 March 1999; accepted 28 January 2000.     

The Effects of Landscape Characteristics on Northern Bobwhite Density

The northern bobwhite (Colinus virginianus) is an ecologically and economically valuable species in the United States. Managers rely on autumn density estimates to set harvest regulations, balancing the interests of hunters and long-term bobwhite population viability. Spatial capture-recapture (SCR) is a useful framework for estimating population size and modeling spatial variation in density. We used SCR to quantify the effect of landscape structure on spatial variation in density for a population of bobwhites on the Di-Lane Wildlife Management Area in Waynesboro, Georgia, USA. Without additional telemetry or nesting data, we were also able to estimate a spatially explicit metric of productivity. To sample the population, we deployed a fixed array of 395, 262, and 268 funnel traps in 2016, 2017, and 2018, respectively. We estimated age structure, with the highest density of juveniles (0.32 birds/ha, 95% CI = 0.28–0.37) and adults (0.10 birds/ha, 95% CI = 0.08–0.12) estimated in 2016. In our top model, density was negatively related to the proportion of closed canopy hardwoods. To increase bobwhite density on the landscape, managers should reduce the amount of closed canopy hardwood forest. Furthermore, the spatially explicit age ratio we estimated could be used to target management towards increasing the recruitment of chicks into the autumn population. An SCR approach may require additional logistical and financial resources relative to other data collection methods, but it makes modeling spatial variation in density straightforward and can be used to gather data to simultaneously understand population structure, vital rates, and movement. © 2021 The Wildlife Society.     

Population Irruptions of Northern Bobwhite: Testing an Age-Specific Reproduction Hypothesis

Abstract: Age-specific reproduction has been suggested for northern bobwhite (Colinus virginianus) and has been hypothesized as a factor contributing to population irruptions. However, little research has been conducted on the subject. We conducted a laboratory and field study to determine if age-specific reproduction occurred in northern bobwhites. Our objectives were to compare 7 reproductive measures (% F nesting, date of first incubated nest, egg-laying rate, nesting rate, clutch size, egg mass, and egg hatchability) between first- and second-year breeders and determine if differential reproduction was impacted by diet quality. The laboratory study consisted of a 2 × 2 factorial experiment with age and diet quality (low protein [12%] and high protein [24%]) as the factors. Data for the field study represented a 6-year data set of bobwhite reproduction (May-Sep 2000-2005) obtained from an ongoing radiotelemetry study in southern Texas, USA. We documented similar productivity (i.e., % F laying, egg-laying rate, and egg mass) and timing of laying (i.e., date of first egg) between juvenile (n = 33) and adult bobwhites (n = 27) in our laboratory study. However, females on the high-protein diet exhibited a greater egg-laying rate than females on the low-protein diet. Under field conditions, we also documented no difference in productivity (% F nesting, nesting rate, clutch size, egg hatchability) and timing of nesting (date of first incubated nest) between age classes (n = 59 juv and 32 ad). Our findings do not support early suppositions of age-specific reproduction in quail. Quail irruptions should not be influenced by population age structure as it relates to age-specific reproduction.     

Gopher Tortoise Response to Habitat Management by Prescribed Burning

ABSTRACT As quality of forested habitat declines from altered fire regimes, gopher tortoises (Gopherus polyphemus) often move into ruderal areas to the detriment of the animal and land manager. We evaluated effects of a dormant-and-growing-season prescribed fire on habitat and gopher tortoise use of degraded longleaf pine (Pinus palustris) forests surrounding military training areas. We burned 4 of 8 sites in winter 2001–2002 and again in April 2003. Changes in vegetation measured during 2001–2004 indicated that burn treatments did not increase herbaceous vegetation. Similarly, movement patterns, burrow usage, and home range of tortoises radiotracked from 2002–2004 did not differ between treatments. Woody cover initially was reduced in the forests postburn, and we found more new burrows in burned forest sites. Once shrub cover was reduced, tortoises started using forested habitat that had become overgrown. However, shrub reduction may be temporary, as woody stem densities increased postburn. Thus, the one-time use of fire to manage tortoise habitat may not rapidly restore the open canopy, sparse woody midstory, and abundant herbaceous vegetation that this species requires. Repeated prescribed fires or additional management techniques may be needed for complete restoration.     

Landscape Connectivity Influences Survival and Resource Use following Long-Distance Translocation of Northern Bobwhite

Translocation is an important component of northern bobwhite (Colinus virginianus) recovery efforts, given the scale of their decline and inability to rapidly recolonize recently restored habitat. Repopulating sites in northern latitudes that are distant from reliable source populations may require long-distance trap and transport from southern locales, potentially compounding existing obstacles for this renascent population recovery technique. The landscape connectivity hypothesis predicts that site fidelity and survival would be lower if release properties are small and fragmented and home range sizes would be smaller and dispersal distances would be lower if habitat quality at the release site is perceived to be high and the surrounding matrix is of low permeability. We evaluated this hypothesis to determine if northern bobwhite survival, site fidelity, and resource selection following translocation differed between 2 contrasting landscapes in the Mid-Atlantic region of the United States. We translocated 508 radio-collared northern bobwhites from northern Florida and southern Georgia, to small, fragmented properties on the eastern shore of Maryland and large, contiguous properties in southern New Jersey, USA. We monitored northern bobwhites via radio-telemetry from approximately 1 April through 30 September, 2015–2018, 2–7 times a week. Breeding season (182 days after release) survival varied among sites, and was generally higher at the 2 New Jersey release sites than at the 2 Maryland sites, yet an acclimation period is ostensibly required to obtain reasonable breeding survival estimates to elicit population growth. Site fidelity, maximum dispersal distances, and home range sizes were lower at the smaller, fragmented Maryland properties than the larger New Jersey properties. These results support the landscape connectivity hypothesis such that reduced connectivity in our study decreased site fidelity and survival. Temporal variation in survival was potentially an artifact of translocation stress or maladaptive behavior during initial acclimation to the release sites, indicating that higher stocking rates may be needed to provide adequate founder abundance for translocation success. Northern bobwhites used early-successional cover at all sites, though selection varied based on scale of analysis and landscape context. These vital rate estimates and resource use patterns should be used to guide future translocations within the Mid-Atlantic, provide perspective for this population restoration technique range wide, and stimulate further investigation into limiting factors. © 2020 The Wildlife Society.     

Effects of Hardwood Reduction Techniques on Longleaf Pine Sandhill Vegetation in Northwest Florida

We tested whether the intensity of hardwood midstory reduction causes commensurate improvements of herbaceous groundcover in fire‐suppressed Pinus palustris (longleaf pine) sandhills. Using a complete randomized block design, we compared the effects of three hardwood reduction techniques (spring burning, application of the ULW^® form of the herbicide hexazinone, chainsaw felling/girdling) and a no‐treatment control on plant species richness, and on life form and common species densities at Eglin Air Force Base, Florida, U.S.A., from 1995 to 1998. ULW^® and felling/girdling plots were burned for fuel reduction two years after initial treatment application. We also sampled the same variables in frequently‐burned reference sandhills to establish targets for restoration. Spring burns achieved partial topkill of oaks (17.6–41.1% from 1995 to 1998) compared to reductions of 69.1–94% accomplished by ULW^® and of 93.2–67.8% by felling/girdling treatments. We predicted that plant species richness and densities of herbaceous groundcover life forms would increase according to the percent hardwood reductions. Predictions were not supported by treatment effects for species richness because positive responses to fire best explained increases in plant richness, whereas ULW^® effects accounted for the largest initial decreases. Legumes, non‐legume forbs, and graminoids did not respond to treatments as predicted by the hypothesis. Again, positive responses to fire dominated the results, which was supported by greater herbaceous densities observed in reference plots. Overall, we found that the least effective and least expensive hardwood midstory reduction method, fire, resulted in the greatest groundcover improvements as measured by species richness and herbaceous groundcover plant densities.     

Supplemental Feeding of Northern Bobwhite Affects Red-Tailed Hawk Spatial Distribution

ABSTRACT Supplemental feeding is a widely used management practice in areas managed for northern bobwhite (Colinus virginianus; hereafter quail). Although food provisioning is intended to benefit quail directly, it may also indirectly affect predators by allowing them to focus on the increased concentration of prey. We studied the effects of food supplementation for northern bobwhite on red-tailed hawk (Buteo jamaicensis) space use in a longleaf pine (Pinus palustris) ecosystem in southwestern Georgia. We used radiotelemetry to determine whether hawks were attracted to areas where supplemental feeding occurred. We found hawks almost 3 times closer to feeding sites (224 ± 96 m; x̄ ± SE) than expected (638 ± 96 m). Our data provide an example of a common game management practice having an unintended influence on a top predator.     

Influence of Anthropogenic Structures on Northern Bobwhite Space Use in Western Oklahoma

ABSTRACT Anthropogenic structures associated with energy development and other activities are a growing concern in wildlife conservation because of habitat loss and fragmentation. We conducted a retrospective analysis of effects of barbed-wire fences, oil-extraction structures, aboveground power lines, resurfaced roads, and artificial water sites on space use by northern bobwhite (Colinus virginianus)in western Oklahoma, USA. Nest location data accrued during 1991–2002 and radiolocation data during 1997–2002. Data suggested fences had a weak repellent effect at distances <300 m, oil structures had neutral effects at distances <800 m, aboveground power lines had neutral effects at distances <250 m, resurfaced roads attracted at distances <350 m, and water sites had neutral effects at distances <250 m. Generally, anthropogenic structures seemed compatible with bobwhite populations on our study area, given density and dispersion of the structures that existed.