Rio Grande Wild Turkeys Research Articles

Urban Green Infrastructure Connectivity: The Role of Private Semi-Natural Areas

Green spaces and blue spaces in cities provide a wealth of benefits to the urban social–ecological system. Unfortunately, urban development fragments natural habitats, reducing connectivity and biodiversity. Urban green–blue infrastructure (UGI) networks can mitigate these effects by providing ecological corridors that enhance habitat connectivity. This study examined UGI connectivity for two indicator species in a rapidly developing city in the southern United States. We mapped and analyzed UGI at a high resolution (0.6 m) across the entire city, with a focus on semi-natural areas in private land and residential neighborhoods. Integrating graph theory and a gravity model, we assessed structural UGI networks and ranked them based on their ability to support functional connectivity. Most of the potential habitat corridors we mapped in this project traversed private lands, including 58% of the priority habitat for the Golden-cheeked Warbler and 69% of the priority habitat for the Rio Grande Wild Turkey. Riparian zones and other areas with dense tree cover were critical linkages in these habitat corridors. Our findings illustrate the important role that private semi-natural areas play in UGI, habitat connectivity, and essential ecosystem services.

Habitat Selection of Female Rio Grande Wild Turkey Influenced by Vegetation and Anthropogenic Structures

The Rio Grande wild turkey (Meleagris gallopavo intermedia) is a popular game species throughout the southcentral United States. It has experienced recent population declines in some areas of its distribution, though the cause is not clear. To better understand Rio Grande wild turkey (hereafter, turkey) ecology and inform management, we attached Global Positioning System transmitters to 34 females in 2016 and 2017. We evaluated habitat selection at both the second-order (landscape) and third-order (home range) scale for the breeding season and second-order selection for the nonbreeding season. Our resource selection function (RSF) models evaluated vegetation, management, and anthropogenic development including oil and gas infrastructure and roads. We found that turkey space use was strongly associated with tall woody cover at both the landscape and home range scale during breeding season and at the landscape scale during nonbreeding season. Additionally, turkey space use was negatively related to the density of oil/gas wells at both scales during the breeding season and at the landscape scale during the nonbreeding season. Turkeys also selected areas close to roads at the landscape scale but avoided high traffic roads within their home ranges during the breeding season. Turkey also chose areas that were >24 mo post fire and close to water sources during the breeding season at both scales. Although turkeys exhibited consistent habitat selection patterns throughout the year relative to trees and oil and gas, our results suggest that their habitat requirements in western Oklahoma are seasonally variable. Management for the Rio Grande subspecies of turkey should maintain tree cover that provides roosting and loafing cover, as well as consider the potential negative impacts of oil and gas infrastructure when locating future energy development.

Molecular Surveillance for Lymphoproliferative Disease Virus and Reticuloendotheliosis Virus in Rio Grande Wild Turkeys (Meleagris gallopavo intermedia) in Texas, USA.

Reticuloendotheliosis virus (REV) and lymphoproliferative disease virus (LPDV) are avian retroviruses that can cause neoplastic disease and present with similar pathologies. Lymphoproliferative disease virus has been reported in the Eastern US and states bordering Texas, USA, but has not been previously detected within the state. In a prior study, we detected REV in native Rio Grande Wild Turkeys (Meleagris gallopavo intermedia) and an Eastern Wild Turkey (Meleagris gallopavo silvestris) originating from West Virginia. Given LPDV detection in states bordering Texas and our finding of an REV-positive Eastern Wild Turkey imported from a LPDV endemic region, we sought to determine LPDV prevalence in Texas and continue surveillance for REV. During 2018-20, dried blood spots from 373 individual Rio Grande Wild Turkeys from 20 different counties were tested for the presence of proviral REV or LPDV DNA. In affected counties, approximately 4% of individuals were infected with REV (7/197) or LPDV (10/273) and one bird was coinfected with both viruses. Phylogenetic analysis indicated a close relationship of the LPDV isolates to variants from other Southern and Central states. This study provides molecular evidence of LPDV in Texas, and continued surveillance is necessary to determine the potential effects of the virus on reproductive success, coinfections, and overall health of Wild Turkey populations.

Phenology‐specific space use by Rio Grande wild turkeys

AbstractConservation of wildlife populations necessitates identifying patterns in space use because fitness requirements influence resource selection; however, details on how phenology affects space use are often only cursorily addressed during development of space‐ and resource‐use estimates. Moreover, space‐use assessments often aggregate distinct, phenology‐specific behaviors into generalized realizations of biological processes, such as reproduction. Therefore, to improve the relevance and accuracy of biological inferences for wild turkey (Meleagris gallopavo) space use at the population level, we defined 12 distinct phenology‐specific periods to compare and contrast variations in space‐use estimates. We calculated 1,568 individual space‐use estimates using dynamic Brownian Bridge movement models for Rio Grande wild turkeys (M. g. intermedia; n = 255 females) across Texas, USA, during 2012−2018. Females in each pre‐laying state used larger areas than during all other phenological states, suggestive of exploratory movements related to reproductive activities and resource acquisition. Incubation core areas were consistently <1.5 ha and incubation range sizes ranged from 10 ha to 48 ha. Core area and range sizes during the brooding period doubled from 15 days after hatch (3.1 ha and 42 ha) to 30 days after hatch (6.5 ha and 89 ha). Post‐breeding and wintering period ranges were >30% smaller than reproductive period ranges. Mean daily distance traveled was similar across phenological states except during incubation and brooding periods. Our results indicate that examining wild turkey space use at identifiable, phenology‐specific temporal scales will help mitigate against biases in estimates of resource selection based on arbitrary phenology definitions that aggregate data across multiple, distinct, phenological states.

Survival, harvest, and population size of Rio Grande wild turkeys in Texas

AbstractUse of band recovery data combined with estimates of hunter harvests provides a foundation for estimation of abundance and population trajectory for a variety of wildlife species. We banded 3,141 Rio Grande wild turkeys (Meleagris gallopavo intermedia) during 2015–2021 and used band‐recovery data to assess annual survival and harvest, and to generate population estimates for male Rio Grande wild turkeys in Texas, USA. Our results indicated male recovery rate was age‐specific (adult = 0.095 ± 0.010 [SE]; juvenile = 0.036 ± 0.009) and adult and juvenile male annual survival was 0.49 ± 0.04 and 0.96 ± 0.14, respectively. Annual survival for adult females (0.68 ± 0.02) was lower than for juvenile females (0.98 ± 0.01). Female recovery rates were not different between fall and spring (0.017 ± 0.004; 0.013 ± 0.003, respectively) and combined harvest rate was 0.009 ± 0.006. Male population estimates, based on hunter harvest estimates, exhibited considerable temporal variation, ranging from 328,185 ± 66,313 in 2016 to 136,700 ± 27,621 in 2020. Using harvest average over the 7‐year study period, we estimated average male abundance was 228,709 ± 46,213. Female population estimates ranged from 895,556 ± 635,146 in 2016 to 409,889 ± 290,702 in 2020. We estimated an average female population of 561,578 ± 396,507. Researchers and managers should continue banding Rio Grande wild turkeys to assess long‐term trends and conduct additional work to confirm the accuracy of harvest estimates in Texas.

Instances of intraspecific nest parasitism in eastern and Rio Grande wild turkeys

AbstractNest parasitism can play an important role in processes regulating population dynamics of both hosts and parasites. Inter‐ and intra‐specific nest parasitism are 2 alternative reproductive strategies observed to occur in about 1% of all bird species. Recently, low productivity in wild turkey (Meleagris gallopavo) populations has resulted in population declines across the southeastern United States. Reproductive output may be influenced by nest parasitism, but the extent of nest parasitism and how it may be related to productivity of wild turkey populations are poorly understood. Herein, we illustrate 6 unreported examples of intraspecific nest parasitism obtained using GPS telemetry data from female wild turkeys in Georgia and Louisiana during 2014−2018. Further, we report 3 occurrences of nest parasitism in Texas using photographic evidence. Our findings suggest that ≥6% of nests are potentially parasitized, and that multiple females may visit and parasitize a single nest. Given recent declines in reproductive output of wild turkeys throughout the southeastern United States, we encourage researchers to continue assessing potential for nest parasitism across wild turkey populations and how this potential may be influenced by predator abundance and activity.

Genome Sequence of Fowlpox Virus-Integrated Reticuloendotheliosis Virus from a Rio Grande Wild Turkey (Meleagris gallopavo intermedia).

ABSTRACTWe report the genome sequence of a nearly intact reticuloendotheliosis virus (REV) insertion within a field strain of fowlpox virus from a Rio Grande wild turkey in Gillespie County, TX. The proviral REV genome comprises 7,943 bp and contains partial long terminal repeats.

Breeding season survival of female Rio Grande wild turkeys in south‐central Texas

AbstractHistorically, Rio Grande wild turkey (Meleagris gallopavo intermedia) density in south‐central Texas has been lower than other regions within the species' Texas range. Within the Oak‐Prairie Wildlife District of Texas, Rio Grande wild turkey harvest regulations are more restrictive for counties in the eastern portion of the district. Due to a perceived increase in turkey density in the eastern portion of the district, Texas Parks and Wildlife Department (TPWD) has considered increasing the spring hunting season harvest bag limit. Because estimates of sex‐specific abundance and male harvest rates are not available, estimates of female driven population parameters such and nest success and female survival can be used to support regulatory decision‐making. Therefore, before a regulation change we evaluated survival of radio‐marked female Rio Grande wild turkeys during the breeding season in 4 counties in the Special 1‐Male zone (hereafter 1‐bird zone) and 2 counties in the South zone (hereafter 4‐bird zone). We captured and monitored breeding season survival for 138 females during 2016–2018, of which 51 were in the 4‐bird zone and 87 were in the 1‐bird zone. Breeding season (1 Mar–14 Aug) naive mortality rate was 23% (19/81) of tagged females in the 1‐bird zone and 32% (14/43) in the 4‐bird zone. The best approximating candidate model for breeding season survival indicated variation in daily survival () was primarily related to daily distance of individual movements ( = 0.998 at average daily distance of 2,471 m). Estimated breeding season survival at the mean daily movement distance was 81% for the 167‐day period. Breeding season survival was similar between the 1‐bird and 4‐bird regulatory zone. Based on our results, female breeding season survival does not seem to be a limiting factor within the Oak‐Prairie Wildlife District of Texas for Rio Grande wild turkeys. We suggest that TPWD focus efforts on supporting landowners to enhance conditions more conducive for reproductive success and suggest future efforts focus on collection of harvest and harvest rate data to estimate population size in lieu of continued monitoring of female reproductive or survival parameters for decision processes.

Hurricane effects on wild turkey survival, daily movements, and roost fidelity

AbstractEnvironmental disturbances driven by global climate variability continue to increase in both frequency and intensity. Recent studies on wild turkeys (Meleagris gallopavo) have documented both direct and indirect demographic effects of short‐term, climatically driven events; however, only limited information is available on the effects of extreme environmental disturbance events on turkey demography. Thus, we evaluated space use and movements of eastern wild turkeys (M. g. silvestris; n = 20) and Rio Grande wild turkeys (M. g. intermedia; n = 22) during hurricane events in South Carolina and Texas, respectively. Hurricane Matthew occurred over a 3‐day period in October 2016 impacting ongoing turkey research on the Webb Wildlife Management Area Complex in South Carolina, whereas Hurricane Harvey occurred over a 5‐day period in August 2017 impacting an ongoing 6‐county study region in Texas. We documented 1 and 2 direct mortalities during Hurricanes Matthew and Harvey, respectively. Mean core area size used by turkeys decreased by 75% during both hurricane events. We did not document evidence of changes in roost fidelity or distance between daily roost clusters after either hurricane. We documented direct mortality of 5 and 8% of the study population during Matthew and Harvey, respectively, and turkeys exhibited a gradient of behavioral responses dependent on hurricane intensity and duration. Because hurricanes can produce substantive modifications to areas used by wild turkeys, we suggest that managers consider initiatives to document legacy effects of extreme environmental disturbance events on local wild turkey demographics, including loss of nesting, brooding and roosting sites.

Old tricks-new opportunities: combining telemetry ellipses and landscape metrics to assess habitat spatial structure

Confidence ellipses are areas derived from telemetry data that can be used to assess daily habitat use when integrated with land cover spatial structure. Our goal was to assess the feasibility of using confidence ellipses derived from telemetry data to assess landscape structure. Our objectives were (1) to identify the geometry of confidence ellipses that can be used in landscape level studies; and (2) to quantify landscape structure within confidence ellipses derived from telemetry data. We used Rio Grande wild turkeys (Meleagris gallopavo intermedia) as our model species. We simulated landscapes and clipped them using known confidence ellipse shapes. We then compared the clipped areas with values measured for our simulated landscapes using landscape metrics that describe landscape structure. We used these results to select ellipse derived from telemetry data to evaluate landscape structure used by wild turkeys during the breeding and wintering seasons in South Texas. Ellipses with a low x/y ratio (< 0.38) had significant differences from simulated landscape measurements. This information was used to remove wild turkey ellipses that did not meet the simulation criteria. Our results suggest that wild turkeys in South Texas used larger, more aggregated and interconnected patches of woody cover during the wintering season than during the breeding season. Landscape simulations facilitate the understanding of how landscape sampling strategies may be affected by sampling shape models. The integration of wildlife telemetry data with landscape ecology approaches and remote sensing were important in identifying spatial patterns used by wildlife.

Small Object Bird Detection in Infrared Drone Videos Using Mask R-CNN Deep Learning

A reliable method to estimate population sizes of wild turkeys (Meleagris gallopavo) using unmanned aerial vehicles and thermal video imaging data collected at several field sites in Texas is described. Automating the data processing of airborne survey videos provides a fast and reproducible way to count wild turkeys for wildlife management and conservation. A deep learning semantic segmentation pipeline is developed to detect and count roosting Rio-Grande wild turkeys (M.g. intermedia) which appear as small faint objects in drone-based thermal IR videos. The proposed approach to detect roosting turkeys that appear as small objects, relies on Mask R-CNN, a deep architecture semantic segmentation algorithm. This is followed by a post-processing data association and filtering (DAF) process for counting the number of roosting birds. DAF was used to eliminate false positives like rocks and other small bright objects, which often have noisy detections across temporally adjacent video frames, that can be filtered using appearance association and distance-based gating across time. Transfer learning was used to train the Mask R-CNN network by initializing using ImageNet weights. Drone-based thermal IR videos are extremely challenging due to the complexity of the natural environment including weather effects, occlusion of birds, terrain, trees, complex tree shapes, rocks, water and thermal inversion. The transect videos were collected at night at several times and altitudes to optimize data collection opportunities without disturbing the roosting turkeys. Preliminary performance evaluation using 280 video frames is promising.

Thermal refuge affects space use and movement of a large-bodied galliform

Temperature affects every organism on Earth and has been argued to be one of the most critical factors influencing organisms' ecology and evolution. Most organisms are susceptible to landscape temperature ranges that exceed their thermal tolerance. As a result, the distribution of landscape features that mitigate thermal extremes can affect movement and space use of organisms. Using Rio Grande wild turkey (Meleagris gallopavo intermedia) as a model species, we measured black bulb temperature throughout the diurnal period and identified vegetation characteristics at wild turkey locations and random landscape locations. We observed that the thermal landscape was highly heterogeneous with temperature varying up to 52 °C at a given ambient temperature. Vegetation type strongly influenced temperature across space during daily peak heating, with taller vegetation types (woody vegetation >2 m) having mean temperatures up to 8.95 °C cooler than the remainder of the landscape. However, these cooler vegetation types were uncommon, only accounting for 8.2% of the landscape. Despite the rarity of tall woody cover, wild turkey showed strong selection for this vegetation type particularly during peak daily heating with 74.9% of locations within 18 m of tree cover. Not only did wild turkey alter space use across time relative to temperature variation, but they also altered movement. We found that on the hottest days (≥35 °C), wild turkeys decreased movement by three fold during peak heating, while movement on cooler days (<30 °C) was uniform. Collectively, our data provide evidence that space use and movement for large avian species can be influenced by the thermal environment, and that the thermal environment is an important component of habitat for a species.

Survey of Reticuloendotheliosis Virus in Wild Turkeys (Meleagris gallopavo) in Texas, USA.

Reticuloendotheliosis virus (REV) is an immunosuppressive and sometimes oncogenic avian retrovirus that establishes lifelong infection in a wide range of avian species. REV-infected wild birds roaming near at-risk captive flocks, such as is the case for the highly endangered Attwater's Prairie Chicken (APC; Tympanuchus cupido attwateri), could act as a reservoir for viral transmission. In wild birds, prevalence rates of REV are low and appearance of associated disease is uncommon. During 2016-17, nearly half of all captive adult APC mortality at Fossil Rim Wildlife Center captive breeding facility in Glen Rose, Texas, US was attributed to REV infection. The unusually high REV prevalence rate prompted us to survey for this virus in wild galliforms throughout the region. From 2016-17, 393 blood samples collected from two subspecies of Wild Turkeys (Meleagris gallopavo) were tested for REV proviral DNA through amplification of the viral 3' long terminal repeat and segments of the viral pol gene. In REV-affected counties, 5% (5/98) of native Rio Grande Wild Turkeys (Meleagris gallopavo intermedia) were identified as REV-positive. In addition, we detected REV in one of 62 Eastern Wild Turkeys (Meleagris gallopavo silvestris) that had been imported during conservation efforts. To better determine protective measures, continued surveillance, including collection and genetic analysis of REV-infected samples, is necessary to identify sources of REV outbreaks in captive APC flocks.

Using dynamic Brownian bridge movement modelling to measure temporal patterns of habitat selection

Accurately describing animal space use is vital to understanding how wildlife use habitat. Improvements in GPS technology continue to facilitate collection of telemetry data at high spatial and temporal resolutions. Application of the recently introduced dynamic Brownian bridge movement model (dBBMM) to such data is promising as the method explicitly incorporates the behavioural heterogeneity of a movement path into the estimated utilization distribution (UD). Utilization distributions defining space use are normally estimated for time-scales ranging from weeks to months, obscuring much of the fine-scale information available from high-volume GPS data sets. By accounting for movement heterogeneity, the dBBMM provides a rigorous, behaviourally based estimate of space use between each set of relocations. Focusing on UDs generated between individual sets of locations allows us to quantify fine-scale circadian variation in habitat use. We used the dBBMM to estimate UDs bounding individual time steps for three terrestrial species with different life histories to illustrate how the method can be used to identify fine-scale variations in habitat use. We also demonstrate how dBBMMs can be used to characterize circadian patterns of habitat selection and link fine-scale patterns of habitat use to behaviour. We observed circadian patterns of habitat use that varied seasonally for a white-tailed deer (Odocoileus virginianus) and coyote (Canis latrans). We found seasonal patterns in selection by the white-tailed deer and were able to link use of conifer forests and agricultural fields to behavioural state of the coyote. Additionally, we were able to quantify the date in which a Rio Grande wild turkey (Meleagris gallopavo intermedia) initiated laying as well as when during the day, she was most likely to visit the nest site to deposit eggs. The ability to quantify circadian patterns of habitat use may have important implications for research and management of wildlife. Additionally, the ability to link such patterns to behaviour may aid in the development of mechanistic models of habitat selection.

Evaluating wild Turkey movement ecology: An example using first‐passage time analysis

ABSTRACTRecent advances in animal tracking technology have increased interest in the field of animal movement ecology. Numerous methods have been developed to extract information from animal movement paths that can be used to link movement behavior to external stimuli such as habitat and climatic conditions. Given the recent development of Global Positioning System (GPS) technology suitable for use on wild turkeys (Meleagris gallapavo), we advocate the adoption of new methodologies to design novel research on wild turkey ecology. Here we provide a worked example using first‐passage time on male Rio Grande wild turkeys (M. g. intermedia) tracked via GPS in South Texas, USA, during April 2009 to illustrate one methodological option on which research can be based. From our example, we infer behavioral decisions in response to habitat variables that varied during the diurnal cycle; turkeys were more likely to exhibit localized movements during midday in open areas near food and water resources. We contend that by taking advantage of GPS technology and focusing research questions on movement behavior, wild turkey research can progress toward answering mechanistic questions regarding turkey habitat use. This shift in research focus will provide much‐needed information to managers that is currently lacking at both local and regional scales. © 2014 The Wildlife Society.

Nest site fidelity and dispersal of Rio Grande wild turkey hens in Texas

AbstractRio Grande wild turkey (Meleagris gallopavo intermedia) nests suffer high predation rates exceeding 65%, which may limit recruitment. We evaluated post‐nesting movements of reproductively active female Rio Grande wild turkeys. We monitored 194 nesting attempts between 2005 and 2010 and documented 17% and 32% overall apparent nest success for the Edwards Plateau and Central Rio Grande Plains study regions, respectively. Rio Grande wild turkey hens move approximately 1.2 km (SD = 0.7) between nesting attempts within a nesting season and approximately 1.4 km (SD = 1.6) between initial nesting attempts among years. Rio Grande wild turkey hens selected open areas with moderate woody cover for nesting (${\bar {x}}$ = 37.7%; range = 3.0–88.2%). Patchiness of vegetation in the nesting landscape also was borne out by typically low edge‐to‐area ratios (${\bar {x}}$ = 0.20; range = 0.040–0.732). We found no clear pattern in movement distance and either landscape composition or edge‐to‐area ratio for within or between breeding season nest site selection for either the Edwards Plateau or Central Rio Grande Plains study region. Based on our results, movement distances post‐nest failure do not seem to influence habitat selection. © 2012 The Wildlife Society.

Retention of butt‐end aluminum leg bands by wild turkeys

AbstractWe examined retention of butt‐end aluminum leg bands on Rio Grande wild turkeys (Meleagris gallopavo intermedia) captured in Texas and Kansas, USA, 2000–2009. We examined 187 recaptured or harvested radiotagged wild turkeys to determine band retention and modeled band retention with Program MARK. We did not detect differences in band retention among age and gender classes or that band retention probability was time dependent. We estimated monthly probability of band retention was 0.990 (SE = 0.002). Band retention probability was 0.971 (SE = 0.006) at 3 months post‐banding and 0.864 (SE = 0.028) at 15 months post‐banding. Butt‐end aluminum leg band retention was not 100% for wild turkeys marked during our work; however, our band retention rates were 3.7–5.7 times greater than described previously. © 2011 The Wildlife Society.

Evaluation of a Global Positioning System backpack transmitter for wild turkey research

AbstractRadiotelemetry is the standard method for monitoring wild turkey (Meleagris gallapavo) movements and habitat use. Spatial data collected using telemetry‐based monitoring are frequently inaccurate due to triangulation error. However, new technology, such as Global Positioning Systems (GPS) has increased ecologists' ability to accurately evaluate animal movements and habitat selection. We evaluated the efficacy of micro‐GPS backpack units for use on wild turkeys. We tested a micro‐GPS developed specifically for avian species that incorporated a GPS antenna with a lightweight rechargeable battery and a very high frequency (VHF) transmitter. We conducted a series of static tests to evaluate performance in varying types of vegetative canopy cover and terrain. After static testing, we deployed micro‐GPS on 8 adult male Rio Grande wild turkeys (M. g. intermedia) trapped in south Texas and 2 adult females trapped in the Texas panhandle. Micro‐GPS units collected 26,439 locations out of 26,506 scheduled attempts (99.7% fix rate) during static testing. Mean distance error across all static tests was 15.5 m (SE = 0.1). In summer 2009, we recovered micro‐GPS from 4 tagged males and both females to evaluate data collection. Units on males acquired approximately 2,500 locations over a 65‐day test period (94.5% fix rate). We recovered units from the 2 females after 19 days and 53 days; those units acquired 301 and 837 locations, respectively, for a 96% fix rate. Cost analysis indicated that VHF will be cost effective when 1 location per day is required up to 181 days, but micro‐GPS becomes less expensive as frequency of daily locations increases. Our results indicate that micro‐GPS have the potential to provide increased reliable data on turkey movement ecology and habitat selection at a higher resolution than conventional VHF telemetric methods. © 2011 The Wildlife Society.

Flooding-induced landscape changes along dendritic stream networks and implications for wildlife habitat

Severe low frequency natural disturbances along stream networks can substantially alter urban and rural landscapes and impact habitat and population dynamics of wildlife species. In 1978, severe flooding along the North Prong of the Medina River significantly altered the habitat for the Rio Grande wild turkey and may have contributed to the decreased abundance of this species observed during recent decades in the southeastern Edwards Plateau, TX, USA. The objective of our study was to examine the changes in landscape structure caused by this flooding event and their potential impact on wild turkey habitat. Aerial photography from 1972, 1984, and 1995 was used to quantify habitat changes in riparian zones and adjacent bottomlands along the Medina River. We documented substantial reductions in habitat suitability and connectivity caused by the flooding, followed by a partial recovery over 17 years. Analysis using patch-level metrics in conjunction with class-level metrics, provided insights to the pattern and possible mechanisms of the landscape changes. Habitat along higher-order streams was most affected, reducing not only the suitable habitat locally, but also the habitat connectivity throughout the riparian network. This loss of connectivity rendered numerous habitat patches along lower-order streams unavailable to Rio Grande wild turkeys as this species depends on riparian corridors for dispersal and movement among habitat patches. Our results illustrate the critical importance of multiple-scale analysis based on hierarchical dendritic structures of river networks when assessing habitat changes and their impact on populations of terrestrial wildlife species dependent on riparian habitats in semi-arid landscapes.

Encounter Rates From Road‐Based Surveys of Rio Grande Wild Turkeys in Texas

ABSTRACT Traditional index‐based techniques have indicated declines in Rio Grande wild turkey (Meleagris gallopavo intermedia; hereafter, wild turkey) populations across much of Texas, USA. However, population indices can be unreliable. Research has indicated that road‐based surveys may be an efficacious technique for monitoring wild turkey populations on an ecoregion level. Therefore, our goal was to evaluate applicability of road‐based distance sampling in the Cross Timbers, Edwards Plateau, Rolling Plains, and South Texas ecoregions of Texas. We conducted road‐based surveys in each ecoregion during December 2007—March 2008 to estimate wild turkey flock encounter rates and to determine survey effort (i.e., km of roads) required to obtain adequate sample sizes for distance sampling in each ecoregion. With simulations using inflatable turkey decoys, we also evaluated effects of distance to a flock, flock size, and vegetative cover on turkey flock detectability. Encounter rates of wild turkey flocks from road‐based surveys varied from 0.1 (95% CI = 0.0–0.6) to 2.2 (95% CI = 0.8–6.0) flocks/100 km surveyed. Encounter rates from surveys restricted to riparian communities (i.e., areas ≤1 km from a river or stream) varied from 0.2 (95% CI = 0.1–0.6) to 2.9 (95% CI = 1.5–6.7) flocks/100 km surveyed. Flock detection probabilities from field simulations ranged from 22.5% (95% CI = 16.3–29.8%) to 25.0% (95% CI = 13.6–39.6%). Flock detection probabilities were lower than expected in all 4 ecoregions, which resulted in low encounter rates. Estimated survey effort required to obtain adequate sample sizes for distance sampling ranged from 2,765 km (95% CI = 2,597–2,956 km) in the Edwards Plateau to 37,153 km (95% CI = 12,861–107,329 km) in South Texas. When we restricted road‐based surveys to riparian communities, estimated survey effort ranged from 2,222 km (95% CI = 2,092–2,370 km) in the Edwards Plateau to 22,222 km (95% CI = 19,782–25,349 km) in South Texas.