Roger D. Applegate

LOCATION AND SUCCESS OF LESSER PRAIRIE-CHICKEN NESTS IN RELATION TO VEGETATION AND HUMAN DISTURBANCE

Abstract Lesser prairie-chicken (Tympanuchus pallidicinctus) populations have declined rangewide, and one of the principal causes is thought to be low nest success. Little is known about the relationship of vegetation structure and human intrusion to lesser prairie-chicken nest location and success. We conducted our study from 1997 to 2002 in southwestern Kansas, USA, on 2 sand-sagebrush (Artemisia filifolia) prairie areas managed for livestock production. We determined apparent nest success (26%) for 200 of 209 lesser prairie-chicken nests located. Nest sites had taller grass, greater sand-sagebrush density, and higher visual obstruction than random locations in the surrounding prairie. We recorded the distances from nests to 6 anthropogenic features (wellheads, buildings, improved roads, unimproved roads, transmission lines, center-pivot irrigation fields) to determine whether the features were related to nest location and success. Sand-sagebrush habitat around 5 of 6 features (all except unimproved roads) was avoided for 80 m (wellheads) to >1,000 m (buildings) by nesting lesser prairie-chickens, but distances to the features were not substantial predictors of apparent nest success. Grass height, sagebrush plant density, and sagebrush height were the most important vegetation characteristics influencing nest success.

The northern bobwhite decline: scaling our management for the twenty-first century

Abstract Northern bobwhites (Colinus virginianus) are one of the most broadly researched and intensively managed species in North America. However, we argue that a disadvantage of this status is that traditional management principles currently are incompatible with the spatial scale necessary to address the nationwide decline in bobwhite abundance. We maintain that halting or reversing this decline will entail 2 principal changes in the scale of management. Primarily we suggest that habitat oversight must switch from historical fine-scale management (promotion of edge habitat, weedy fencelines, disked strips, living hedges, and food plots) to regional management of usable space. Secondly, within these regional management areas, we should apply harvest management that employs risk-sensitive strategies that conservatively avoid undermining the primary goal. This entails narrowing the scale of harvest management from statewide to regional levels. If these ideological changes cannot be made and historical policies remain in force, we risk failing to stabilize, let alone increase, bobwhite populations.

Demographic Sensitivity of Population Change in Northern Bobwhite

Abstract The northern bobwhite (Colinus virginianus) is an economically important gamebird that is currently undergoing widespread population declines. Despite considerable research on the population ecology of bobwhites, there have been few attempts to model population dynamics of bobwhites to determine the contributions of different demographic parameters to variance of the finite rate of population change (λ). We conducted a literature review and compiled 405 estimates of 9 demographic parameters from 49 field studies of bobwhites. To identify demographic parameters that might be important for management, we used life-stage simulation analyses (LSA) to examine sensitivity of λ to simulated variation in 9 demographic parameters for female bobwhites. In a baseline LSA based on uniform distributions bounded by the range of estimates for each demographic parameter, bobwhite populations were predicted to decline (λ = 0.56) and winter survival of adults made the greatest contribution to variance of λ (r2 = 0.453), followed by summer survival of adults (r2 = 0.163), and survival of chicks (r2 = 0.120). Population change was not sensitive to total clutch laid, nest survival, egg hatchability, or 3 parameters associated with the number of nesting attempts (r2 <0.06). Our conclusions were robust to alternative simulation scenarios, and parameter rankings changed only if we adjusted the lower bounds of winter survival upwards. Bobwhite populations were not viable with survival rates reported from most field studies. Survival rates may be depressed below sustainable levels by environmental conditions or possibly by impacts of capture and telemetry methods. Overall, our simulation results indicate that management practices that improve seasonal survival rates will have the greatest potential benefit for recovery of declining populations of bobwhites.

Age‐Specific Survival and Probable Causes of Mortality in Female Lesser Prairie‐Chickens

Abstract Long-term population declines and habitat reductions have increased concern over the status of the lesser prairie-chicken (Tympanuchus pallidicinctus). Robust estimates of demographic parameters are essential for identifying population declines and planning effective management. We evaluated the effects of age and season on the survival of female lesser prairie-chickens at 2 sites in southwestern Kansas, USA. Using telemetry data from a 7-year field study (from 1997 to 2003), we estimated seasonal (Apr–Sep) and annual (Apr–Mar) survival. We also examined daily survival rates of females attending nests during the 26-day incubation period and young during the 14-day early brood-rearing period. We evaluated the probable mortality causes of radiomarked birds by examining evidence at recovery sites. We captured 227 female lesser prairie-chickens (87 yearlings, 117 ad, and 23 age undetermined) and fitted them with radiotransmitters. Estimates of 12-month survival were lower among yearlings (Ŝ12 = 0.429, SE = 0.117) and adults at site I (Ŝ12 = 0.302, SE = 0.080) than among yearlings (Ŝ12 = 0.588, SE = 0.100) and adults at site II (Ŝ12 = 0.438, SE = 0.083). The patterns in timing of mortality and age-specific 6-month survival were consistent with those of 12-month estimates at site I from 1998 to 2002, with a peak in mortality during May and June. Females tending to nests or to prefledged chicks had lower daily survival (DŜRtend = 0.993, SE = 0.001) than females not involved in these activities (DŜRfailed-breeder = 0.997, SE = 0.002). We recorded 92 mortalities from April 1997 to March 2003, and 59% and 11% were attributed to predation by mammals and raptors, respectively. Our research suggests that predation during the nesting season can have a major impact on lesser prairie-chicken demography, and conservation efforts should focus on enhancing female survival during the nesting and brood-rearing seasons.

Optimal group size and northern bobwhite coveys

Abstract Northern bobwhite, Colinus virginianus , form social units, called coveys, during the nonbreeding season (approximately September–April). Because the evolutionary advantage of this behaviour is generally unknown, we used controlled group size manipulations within an aviary to investigate whether group size influences (1) the time that the covey spends feeding, (2) the percentage of the covey that is vigilant, (3) the overall vigilance of the group and (4) the time to predator detection. We found that increasing group size increased the time that coveys spent in an exposed feeding area, reduced individual vigilance, improved group vigilance and decreased the time to detection of a potential predator. Additionally, we used experimental reductions of wild northern bobwhite coveys to test whether groups size influences (1) individual and covey survival, (2) daily movement in maintaining covey size and (3) mass change. We conducted field research on 12 independent 259-ha study areas (6 control plots and 6 treatments, where 60% of the population was removed) in east-central Kansas, U.S.A. between 9 November and 31 January, 1997–2000. We radio-marked 386 radiocollared individuals that comprised 137 groups on the study areas. Covey size did not differ between or within years or treatments ( X ±SE: 10.98±0.22 individuals). Our results indicate that a stable group size existed between 1 and 22 individuals, with 11 being an optimal group size. Small coveys (1–7 individuals) had lower group persistence and individual survival, and used increased movement to create or join larger groups where survival was higher. Large groups (15–22) had lower individual survival, increased group movement and individual mass loss. Density-dependent feedbacks (e.g. lower survival and increased competition) may have lowered larger coveys to a stable size. Our results suggest the regulation of an optimal covey size of 11 was promoted by high group persistence, low group movement, improved feeding efficiency, improved individual predator detection and improved individual survival. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.

WINTER SURVIVAL AND ADDITIVE HARVEST IN NORTHERN BOBWHITE COVEYS IN KANSAS

Abstract We examined how harvest affected natural mortality rates and how the dynamics of northern bobwhite (Colinus virginianus, hereafter bobwhite) covey membership might affect the additive nature of harvest. We conducted repeated searches for coveys and radiomarked all coveys found on 12 259-ha study areas in east-central Kansas, USA. We simulated a harvest in 6 randomly selected areas each year during November–January, 1997–2000, by trapping and removing 60% of bobwhites in each covey. We used flush counts and radiotelemetry to measure harvest effects on natural mortality rates, overall winter survival, covey size, and densities. Observed natural mortality rates of radiomarked individuals were similar between harvested (50.6 ± 4.3%) and unharvested areas (52.1 ± 4.7%). Estimated winter survival was 47.9% on the unharvested areas and 20.9% on the harvested areas. Harvest did not affect the number of coveys, average covey size, or density of bobwhites, indicating that coveys coalesced through local movement. Our results indicate that harvest is additive to natural mortality and suggest that local movement to maintain optimal group sizes can mask the true effect of harvest on observed densities in small areas.

Spatial Variation in Lesser Prairie-Chicken Demography: A Sensitivity Analysis of Population Dynamics and Management Alternatives

Abstract The lesser prairie-chicken (Tympanuchus pallidicinctus) is currently considered a candidate for protection under the Endangered Species Act. To identify potential limiting factors for lesser prairie-chicken populations, we developed an age-based matrix model of lesser prairie-chicken population dynamics to compare the relative importance of components of reproduction and survival, and determine if various management alternatives stabilize or increase rates of population change. We based our analyses on an intensive 6-year population study from which demographic rates were estimated for each age class in Kansas. We used deterministic models and elasticity values to identify parameters predicted to have the greatest effect on the rate of population change (λ) at 2 study sites. Last, we used life-stage simulation analysis to simulate various management alternatives. Lambda was <1 for both populations (site 1: λ  =  0.54, site 2: λ  =  0.74). However, we found differences in sensitivity to nest success and chick survival between populations. The results of the simulated management scenarios complemented the lower-level elasticity analysis and indicated the relative importance of female survival during the breeding season compared with winter. If management practices are only capable of targeting a single demographic rate, changes to either nest success or chick survival had the greatest impact on λ at site 1 and 2, respectively. Management that simultaneously manipulated both nest success and chick survival was predicted to have a greater effect on λ than changes in survival of adult females. In practice, our demographic analyses indicate that effective management should be based on habitat conservation measures to increase components of fecundity.

NESTING ECOLOGY OF LESSER PRAIRIE-CHICKENS IN SAND SAGEBRUSH PRAIRIE OF SOUTHWESTERN KANSAS

Abstract Despite the fact that the Lesser Prairie-Chicken (Tympanuchus pallidicinctus) is a species of conservation concern, little is known about its nesting ecology, particularly in sand sagebrush (Artemisia filifolia) habitats. To find and monitor nests, we captured and equipped 227 female Lesser Prairie-Chickens with transmitters (87 yearlings, 117 adults, and 23 of unknown age) from 1997 to 2002 in southwestern Kansas. Apparent nest success was similar for yearlings (31%, n = 74) and adults (27%, n = 97) but differed marginally (P = 0.090) between first nests (29%) and renests (14%). An estimated 31% of females that were unsuccessful in their first nesting attempt initiated a second nest. The probability that a female would initiate a second nest after failure of the initial attempt was negatively influenced by the day of incubation on which the initial attempt failed. Over 95% of all nests were initiated and completed between 5 May and 2 July. The primary cause of nest failure was predation by coyotes (Canis latrans) and gopher snakes (Pituophis melanoleucus). Mean clutch size, egg fertility, hatching success, nesting and renesting frequency, and incidence of interspecific parasitism were all similar across years and between yearlings and adults. Distances between nest sites were used as an index to nest-site fidelity between first nests and renests and for across-year nesting attempts. Mean distances between first nests and renests were similar for yearlings (1,071 m) and adults (1,182 m). Mean distance between nests constructed by the same female in subsequent years (918 m) did not differ between age classes or success of the first years nest. Most females (80%) nested closer to a lek other than the lek where they were captured.

Lesser prairie-chicken brood habitat in sand sagebrush: invertebrate biomass and vegetation

Abstract Invertebrates are an important food source for grouse chicks, especially within the first 2 weeks of life. Invertebrate abundance is highly patchy and dependent upon herbaceous cover and vegetation structure. We examined the relationship between invertebrate biomass (from sweepnet samples) and habitat structure at lesser prairie-chicken (Tympanuchus pallidicinctus) brood-use and non-use areas during 2001 and 2002 in a sand sagebrush (Artemisia filifolia) prairie vegetation community of southwestern Kansas. We delineated use and non-use areas from paired sampling points within and outside 95% utilization distributions of radiomarked brood females, respectively, during the first 60 days post-hatch. We measured vegetation cover and invertebrate biomass (Acrididae and “other” invertebrates) at 71 paired points on 2 study sites (Site 1=4 broods, Site 11 = 12 broods). Both Acrididae and other invertebrate biomasses were greater at brood areas than non-use areas on both study sites, suggesting this food source likely had a greater influence on brood habitat use than vegetation type. Vegetation structure described brood-use areas better than vegetation type because brood-use areas had greater visual obstruction readings (VORs) than non-use areas regardless of dominant cover type. We also examined the predictive relationship between vegetation type and invertebrate biomass. Sand sagebrush density was the best linear predictor of Acrididae biomass, with lower densities having the greatest Acrididae biomass. We propose experiments to determine best management practices that produce abundant invertebrate biomasses for lesser prairie-chicken brood habitat, using our study as a baseline.

Radiotelemetry Survival Estimates of Lesser Prairie-Chickens in Kansas: Are There Transmitter Biases?

Abstract Radiotelemetry has provided wildlife biologists with a tool to estimate survival where fates of individuals likely are known. Analyses of known-fate data can yield accurate survival estimates if 5 assumptions are met. Two of these assumptions are rarely tested: that transmitters have no effect on survival of study animals and that right-censoring (i.e., any animal not located is as likely to be alive as dead) is random with respect to the survival of study animals. Using joint-models originally developed for live-encounter and dead-recovery data, we examined the potential for bias in survival estimates of radiomarked male lesser prairie-chickens (Tympanuchus pallidicinctus) in a 3-year study in southwestern Kansas, USA. Additionally, we examined the potential bias of right-censoring by comparing the return rates of known-fate and right-censored individuals. We captured 216 male lesser prairie-chickens and marked them with a combination of leg bands and a radio (n = 72) or leg bands only (n = 144). We applied joint-models to capture histories based on live-capture and telemetry data. The model best supported by the data indicated that 6-month survival was constant (Ŝc = 0.679, SE = 0.050) across radiomarked and banded birds. Eight of 16 (50%, SE = 12.5%) right-censored birds not detected because of radio failure were subsequently recaptured, which was not different from the return rates for known-fate birds (23 of 59; 39%, SE = 6.3%). Survival estimates of male lesser prairie-chickens in this study were not measurably biased by radiomarking, as their survival was greater than or equal to those of banded birds, and right-censored birds had similar return rates to those of known-fate individuals. Our results are encouraging because they indicate that 2 critical assumptions underlying analyses of known-fate data can be met with radiotransmitters and attachment techniques currently used in field studies of wild populations of lesser prairie-chickens.