Quail Management: Issues, Concerns, and Solutions for Public and Private Lands - A Southeastern Perspective

Biologists generally assume that habitat loss, fragmentation, and conversion resulting from changes in landuse are primarily responsible for the nearly rangewide declines in northern bobwhite (Colinus virginianus) abundance noted since at least 1990. Few data-based analyses have addressed this relationship at broad spatial scales. We used data on northern bobwhite abundance from the North American Breeding Bird Survey (BBS; 1966–1999) and county-level landuse from the U.S. Census of Agriculture (COA; 1978, 1987, 1997) to evaluate how 9 landuse variables related to northern bobwhite abundance at the rangewide spatial scale. We also explored the relationship between cropland cover and northern bobwhite abundance by state, physiographic region, and using a moving window approach. Although northern bobwhite abundance typically decreased at the rangewide spatial scale, trends in abundance varied considerably spatially, either exhibiting no trend or increasing in many western and northern portions of this species’ range. While both spatial and temporal patterns in landuse were obvious, there were no clear univariate or multivariate relationships among these variables and bobwhite abundance that could be applied universally across this species’ range. The relationship between cropland cover and northern bobwhite abundance based on physiographic regions was more interpretable than that based on political boundaries (states). When data were used to define spatial patterns between cropland cover and northern bobwhite abundance, spatially consistent and temporally persistent patterns were obtained. We suggest that further research using moving windows of various dimensions, including landuse variables in addition to cropland, and adding several more decades of bobwhite and landuse data is an essential aspect of formulating defensible, spatially explicit strategies for northern bobwhite conservation and management

Broad-Scale Relations between Conservation Reserve Program and Grassland Birds: Do Cover Type, Configuration and Contract Age Matter?

The Conservation Reserve Program (CRP) is a voluntary cropland set-aside program where environmentally-sensitive cropland is retired to a conservation practice. Grassland birds should benefit because most CRP is grass habitat and because amount of land in CRP is highest in agriculture-dominated areas of the United States where grassland habitat has been most impacted. We used the Breeding Bird Survey and Common Land Unit (CLU) data (spatially-explicit data of farm field boundaries and land cover) to identify relations between types and configurations of CRP and grassland bird abundance in 3 Midwestern states. All 13 species we studied were related to at least one aspect of CRP habitat - specific conservation practices (e.g., native vs. exotic grass), CRP habitat configuration, or habitat age. Treating all types of CRP as a single habitat type would have obscured bird-CRP relations. Based on our results, creating a mosaic of large and small set-aside patches could benefit both area-sensitive and edge-associated grassland birds. Additionally, northern bobwhite and other birds that use early successional grasslands would benefit from periodic disturbances. CRP, agrienvironment schemes, and other government-sponsored set-aside programs may be most successful when administered as part of a targeted, regional conservation plan

Population Response of Northern Bobwhite to Field Border Management Practices in Mississippi

Empirical relationships of the intensity and spatial extent of field border management required to elicit measurable population responses of northern bobwhite are needed. We established 90.5km of herbaceous field borders (6.1 m wide) along row crop field edges on one half of each of 3 - 800-ha agricultural landscapes in northeast Mississippi. Mean percentage of row crop fields established in field borders was 6.0%. During 2000 - 2002, we measured breeding season abundance and fall density on all 3 sites and survival of radiomarked bobwhite on 2 of the 3 sites. We used space-use models of bobwhite habitat composition and configuration to estimate changes in habitat suitability resulting from field border implementation. Breeding season survival did not differ between bordered (S = 37.2, SE = 0.06) and non-bordered (S = 42.7, SE = 0.09; Χ1^2 = 0.001, P = 0.97) sites. Moreover, bordered and non-bordered sites did not differ significantly with respect to breeding season call counts (bordered = 1.0, SE = 0.18; non-bordered = 0.8, SE = 0.27; F1,10 = 0.44, P = 0.22) and fall density (bordered = 0.2 birds/ac, SE = 0.07; non-bordered = 0.1 birds/ac, SE = 0.05; F1,10 = 2.18, P = 0.17). However, field borders increased the amount of usable space on average up to 13.1% on bordered landscapes. The relatively low percentage of field borders established on our sites was not sufficient to elicit measurable population responses of bobwhite. We recommend at least 5-10% of a study area be placed in field border habitats to enhance local bobwhite populations

The Law of Interspersion and the Principle of Edge: Old Arguments and a New Synthesis

Leopold’s interspersion hypothesis has experienced fluctuating acceptance, opposition and neglect due to its unintentional ambiguous description and seemingly simplistically universal application. Originally developed to describe the positive association between animal density and habitat heterogeneity in the landscape, the hypothesis has been mischaracterized as the principle of edge resulting from Guthery and Bingham’s (1992) assertion that the interspersion hypothesis could be modeled by the amount of ‘high contrast’ edge and that edge density and interspersion were synonymous. We contend that Leopold’s original intention was not to promote more edge density is always better but rather to promote interspersion of habitat types within landscapes suitable for bobwhite. We argue that edge density and interspersion are different metrics to describe landscape configuration but are incorrectly used interchangeably. These metrics reflect two unique hypotheses regarding bobwhite relationships with landscape structure. We used a northern bobwhite (Colinus virginianus) monitoring dataset to demonstrate the importance of the proper use of edge density and interspersion metrics. We modeled bobwhite abundance at 160 sites across 6 years using an open N-mixture model. We used Fragstats to calculate edge density and interspersion at the landscape scale. These metrics were not correlated (r \u3c .10) indicating they describe unique aspects of configurational heterogeneity. Both metrics had positive but varying effects on bobwhite abundance. We recommend scientists have explicit a priori hypothesis regarding the differential effects of edge density and interspersion

Effects of Northern Bobwhite Habitat Management Practices on Red Imported Fire Ants

Management practices that create early successional plant communities through disturbance (discing and prescribed fire) often are prescribed for restoration of declining northern bobwhite (Colinus virginianus) populations. Because disturbance may facilitate invasion of exotic flora and fauna such as red imported fire ants (RIFA, Solenopsis invicta), we hypothesized that habitat management practices commonly used to enhance bobwhite habitat might have the unintended consequence of increasing local abundance of RIFA. During 1999, we tested effects of 4 treatments (spring discing, spring prescribed burning, spring mowing, and no management), in a randomized complete block design (n = 10) on RIFA abundance in Conservation Reserve Program (CRP) fields in central Mississippi. We surveyed RIFA abundance using 3 measures: 1) mound density, 2) a population index based on worker ant and brood estimates, and 3) foraging activity as indexed by attraction to protein bait cups. During May 1999, mound density (P = 0.0136) and population index (P 0.0078) differed among treatments, with abundance values greatest in plots treated with fire, and lowest in disced plots. The index of foraging activity did not differ among treatments (P = 0.6637). During October 1999, mound density (P = 0.0334) and population index (P = 0.0451) differed among treatments with abundance values greatest in plots receiving fire and disc treatments, and lowest abundance in control plots. The index of foraging activity did not differ among treatments (P = 0.9079). Disturbance tools such as prescribed fire and discing are essential to maintain plant communities to which bobwhite are adapted; however, they may have the unintended consequence of facilitating invasion of RIFA and increasing local RIFA populations

Effect of Temperature and Wind on Metabolism of Northern Bobwhite in Winter

Northern bobwhite (Colinus virginianus) are widely distributed across more than half of the United States, and extending into Canada and Mexico. Within this distribution they tolerate a wide range of climatic conditions and thermal stress. Annual variation in weather can produce dramatic short-term population fluctuations, particularly in the northern portion of the distribution. To better understand effects of thermal stress on energy requirements of bobwhite, we measured roosting metabolic response to cold stress and wind speed using open respirometry in a closed-circuit wind tunnel. Oxygen consumption was measured for 8 winter-acclimated captive bobwhites at each of 8 temperatures (-15°, -10°, -5°, 0°, 5°, 10°, 20°, and 30° C) at free convection and at 3 wind speeds (0, 1, and 2 m/sec) at -15° and 0° C. Over the range of body mass we measured (201.5 ± 1.3 g, n = 64), metabolic rate varied with body mass (P \u3c 0.001) but did not differ between sexes (P = 0.187). Mean standard metabolic rate (V02) was 3.4 ± 0.11 mL O2/minute/bird (0.0171 ± 0.0004 mL O2/ min/g) or 1.14 ± 0.04 W/bird. Below a lower critical temperature of 24.1° C, metabolic rate was linearly related to operative temperature (Te)(V02 = 7.187 - 0.1568[Te]; r2 = 0.86, P \u3c 0.001). Metabolic rate (M–E) was linearly related to wind speed (WS) at -15° C (V02 = 9.741 + 0.4609[WS]; r2 = 0.99, P = 0.001) and 0° C (V02 = 6.713 + 0.4609[WS]; r2 = 0.99, P = 0.001). We discuss implications of these energy expenditures in the context of current research and management

Foraging Behavior of Northern Bobwhites in Relation to Resource Availability

Distribution of food resources may influence northern bobwhite (Colinus virginianus) foraging decisions and demographic rates. We tested whether covey movements were sensitive to food availability by spreading sorghum (Sorghum bicolor) every 15 days at 3 rates; high rate (174 L/ha/yr), low rate (44 L/ha/yr), and no feed on 3 sections (~240 ha each) of Tall Timbers Research Station, 2009–2010. We measured sorghum availability spread along a 17 km feeding trail every 5 days. We determined seasonal (1 Nov - 15 Mar) home ranges of radio-tagged coveys (n = 89) and daily movement rates and home ranges of a subset of coveys located every 30 mins, sunrise to sunset (1 Feb - 15 Mar). Diet was determined from harvested bobwhites. Mean sorghum availability (seeds/0.5m2) on the feed trail declined from 50 seeds at day 1 to 12 seeds at day 15, and 11 seeds at day 1 to 0 seeds at day 10, for high and low rates, respectively. Seasonal home ranges did not differ among treatments; however, daily home ranges were smaller for coveys on the high rate areas, as was dispersion of locations within home ranges. Distances to the feed trail from covey and random locations were similar. There was no difference in distance traveled (25.20 m; SE = 0.65) between consecutive covey locations among treatments. Proportion of sorghum in the diet declined precipitously when \u3c15 seeds/0.5m2. We estimated an empirical giving up density of 10–14 seeds/0.5m2, ~1.6 kcals/0.5m2. Food availability, even at high levels, marginally affected covey space use and movement rates during late winter. Other factors affecting bobwhites, such as predator avoidance, or thermal regulation, may have a more significant effect on bobwhite covey daily movements and space use

Annual Variation in Northern Bobwhite Survival and Raptor Migration

We estimated survival of radio-marked northern bobwhite (Colinus virginianus) on a managed prairie site in northeast Mississippi during 2 disparate winters (15 Sep-14 Apr 2000–2002). We retrospectively examined factors that may influence bobwhite survival. Pooled survival rates differed substantially between years (S 1⁄4 0.03 6 0.02 in 2000–2001 and S 1⁄4 0.36 6 0.16 in 2001–2002). Regional relative abundance of 3 species of raptors thought to be important predators of bobwhite was greater during 2000 compared to 2001 based on kriging of Christmas Bird Count (CBC) data. We demonstrate an approach for characterizing annual variation in spatial distribution of migratory raptors and suggest that annual variation in local winter predator context may be useful for explaining annual variation in winter survival of local bobwhite populations

Estimating Sample Sizes for Distance Sampling of Autumn Northern Bobwhite Calling Coveys

Point transect sampling of calling coveys has been advocated for estimating autumn abundance of northern bobwhite (Colinus virginianus; hereafter bobwhite). We conducted power analysis, over a range of expected bobwhite calling covey densities to determine levels of sampling required to obtain density estimates for calling coveys over a wide range of precision. We used distance/detection information for autumn bobwhite coveys from 701 observer-mornings on 39 farms in the Upper Coastal Plain of Georgia to construct a global detection function (Uniform with cosine adjustment) using Program DISTANCE. We used simulation models to determine the expected coefficient of variation (CV) on density in relation to number of points sampled. We generated 1,000 sets of random samples in increments of 10 at sample sizes of 10-1,000. At each sample size we generated the respective number of observations from a Poisson distribution with λ = 0.5-3.0 and computed the density and associated statistics using the global detection function. We report the mean CV on covey density at each sample size. As expected, the CV on density decreased with increasing sample size and expected number of detections per point. Assuming sufficient observations to estimate the detection function, a CV on density \u3c15% could be achieved with 50 points at densities with a mean detection of 1 covey/point or 20 points with a mean detection of 2 coveys/point. A mean CV \u3c10% required 100 points at 1 covey/point and 30 points at 2 coveys/point. These simulations demonstrate that distance-based autumn covey surveys can provide density estimates for calling coveys with reasonable precision given sufficient effort