Global Positioning System Transmitters Research Articles

Predicting anthropogenic food supplementation from individual tracking data

Many wildlife species consume food or refuse provided by humans. To understand the effect of anthropogenic food subsidies on wildlife populations, we first need to quantify where and when individuals can access such food sources. The Red Kite Milvus milvus is an opportunistic raptor species and uses both inadvertent and deliberate food subsidies provided by citizens. Here we present a new approach using global positioning system (GPS)‐tracking data to predict where anthropogenic food subsidies probably occur. We tracked 497 individuals with solar‐powered GPS transmitters over an average of 3.2 (range 1–9) breeding seasons in Switzerland, and combined these data with locations of 125 known feeding sites obtained through interviews. We used two sequential random forest models, at both individual movement and population levels, to predict where anthropogenic food subsidies were attended by Red Kites. The first model classified locations that were frequently and regularly revisited, and successfully predicted 85% of locations that were within 50 m of an externally validated feeding site. These predicted locations were aggregated in 500‐m grid cells to calculate the proportion of individuals and locations associated with predicted food subsidy. A second model related the presence of known food subsidies to the aggregated predictions. In our study area, 80% of known anthropogenic food provision locations could be correctly identified using Red Kite tracking data, but data sparsity beyond the core range of tracked individuals limits predictions of anthropogenic food subsidies at larger geographical scales. Nonetheless, biologging data can identify ephemeral food sources, and facilitate an assessment of the importance of anthropogenic food subsidies for the fitness of individuals in tracked populations.

Jaguar predation on domestic horses in the dry forest of northwestern Costa Rica

AbstractDepredation of domestic horses (Equus caballus) by jaguars (Panthera onca) is an example of human–wildlife conflict that has not received much attention. We monitored spatio‐temporal activity and distribution of horses in a 2.64‐km2 fenced area in the dry forest of northwestern Costa Rica in response to 16 jaguar killings of horses during January‐November 2017. We monitored 4 horses (2 males, 2 females) equipped with global positioning system transmitters from February‐September 2018 to identify daily and seasonal patterns of use of cover types and a water source by horses. We then compared these results to the previous locations where jaguars killed horses to identify the circumstances under which horses seemed more vulnerable to jaguar predation. Based on 1,693 locations, horses spent most time in grassland (92%) rather than forest and edge vegetation (8%) and used a core area of 0.74 km2 (kernel density estimation) to 0.86 km2 (minimum convex polygon). Of 16 horse predation events by jaguars, 9 events (56%) occurred in grasslands, 4 in forested areas (25%), and 3 in the forest edge (19%), indicating predation events occurred disproportionately from expected counts based on horse use of vegetation. The predation sites were characterized by a higher proportion of edge and a lower proportion of forest compared to a random points. We suggest that when horses explored areas near the edge of forested areas, the chances of being preyed on by jaguars increased.

Sex‐specific resource use by wild turkeys in response to hunting activity

AbstractHunting causes direct mortality and potentially disrupts normal activities of game and non‐game species. As spatial (i.e., selection of hunting areas) and temporal (i.e., only diurnally present) patterns of hunters can become predictable, hunted species may respond accordingly. Risk becomes more dynamic and complex for species that are hunted concurrent with their breeding cycle, and growing literature has noted that wild turkey (Meleagris gallopavo spp.) behaviors can be altered by hunting activity. We allocated global positioning system (GPS) units to 1,500 wild turkey hunters and affixed GPS transmitters to 175 wild turkeys during 2014–2018 on the Webb Wildlife Management Area Complex in South Carolina, USA. We evaluated whether wild turkeys shifted resource selection as a function of hunter resource selection during the progression of hunting seasons. Male wild turkeys avoided areas where stationary hunting bouts occurred during the early hunting season (and selected for these areas before hunting began), whereas females were more likely to select those areas avoided by males by the end of the hunting season. For every 15% increase in predicted probability of an area being hunted, male wild turkeys were 4.16 times less likely to select that area, whereas female wild turkeys were 1.08 times more likely to select that area relative to pre‐season periods when hunters were not on the landscape. Hunting activity induced immediate responses by male wild turkeys as they sought refuge away from hunted areas. Coupled with recent research suggesting hunters are more influential than natural predators in reducing the frequency of male vocalizations and eliciting fleeing and avoidance behavior, our results indicate hunting activity could affect distribution and courtship behaviors of male wild turkeys during their breeding season.

Large- and Small-Scale Climate Influences Spring Migration Departure Probability of American White Pelicans

Endogenous (e.g., age and sex) and exogenous (e.g., climate and resource availability) factors influence avian migration phenology. However, little is known regarding the migration ecology of birds at the non-breeding grounds, including the American white pelican (Pelecanus erythrorhynchos). We used Global Positioning System transmitters to track the movements and migration of 51 pelicans from 2002 to 2012. We used the Kaplan–Meier model to estimate pelican spring migration probabilities to quantify partial migration with 94 spring migration events and used the Cox proportional hazards model to evaluate the effects of the North Atlantic Oscillation index (NAOI), Southern Oscillation Index (SOI), and spring daily precipitation on the propensity of pelican spring migration departures. Increases in the NAOI and SOI enhanced the propensity of pelican spring departure. The propensity of spring departure was also positively related to daily precipitation. Male pelicans have greater spring migration probabilities than female pelicans. Spring migration departure probabilities of adult pelicans are greater than those of immature pelicans. Therefore, both large-scale and local climatic conditions affect pelican spring departure probabilities. Advanced migratory phenology of pelicans caused by climate changes with warming temperature and increased precipitation may result in the mismatch of pelican spring arrival with food resource availability of breeding grounds and subsequent pelican population declines.

Estimation of GPS transmitter antenna phase center offsets by integrating space-based GPS observations

The deviations of the microwave signal transmitting point of Global Navigation Satellite Systems (GNSS) satellites with respect to the corresponding center-of-mass were and still are significant bias sources for GNSS-based terrestrial reference frames (TRF). Satellite phase center offsets (PCOs) and variations (PVs) are usually derived from GNSS observations from the tracking network of the International GNSS Service (IGS). Because of the strong correlation between the scale of the TRF and the satellite PCOs in the z-direction (z-PCOs), a no-net-scale (NNT) condition relative to, for instance, the International Terrestrial Reference Frame (ITRF) is commonly applied. One approach for estimating transmitter phase centers without constraining the scale is to consider space-based GNSS observations. Within this study, we estimate the satellite PCOs of the Global Positioning System (GPS) based on zero-difference ionosphere-free observations from six low Earth orbiters (LEOs) and ground networks with different numbers of stations. The six LEOs are different in their orbits, GPS receiver equipment, and tracking characteristics. We jointly estimate orbits, station coordinates, and GPS satellite PCOs in an integrated processing. The horizontal offsets are shown to significantly benefit from the LEOs onboard observations by reducing the correlation between these offsets and the GPS satellite orbit and attitude. Without applying a no-net-scale condition to the ground network, the GPS z-PCOs are estimated. By adding six LEOs, the correlation coefficients between the GPS z-PCOs and the scale is reduced significantly (about from 0.85 to 0.3), consequently, the precision of estimation is improved. When including the six LEOs, the GPS z-PCOs estimated without applying NNS are very stable. The estimated GPS z-PCOs have a −231 mm difference in average to the values in igs14_2134.atx and the corresponding scale to IGS14 reference frame is +1.89 part per billion. The estimated GPS z-PCOs agree with previous studies based on Swarm satellites and Galileo. The improvement due to different numbers of LEOs and the impact of LEO z-PCO errors on the estimation are discussed.

Improved 2D Ground Target Tracking in GPS-Based Passive Radar Scenarios.

Global Positioning System (GPS) satellites offer promising opportunity for Passive Radar systems due to their global coverage and the availability of multiple satellites throughout the world. However, their low power at ground level limits system coverage. In this paper, a GPS based Passive Radar which exploits a single illumination source, and uses digital array processing for ground targets localization is presented. To face signal power problems, a processing scheme combining reconstructed reference signals, adaptive filtering techniques and spatial filtering is implemented. Conventional beamforming techniques are used to increase the level of the target echo before the detection stage, and high resolution DoA estimation techniques are applied to estimate targets azimuth. Ground target localization in local Cartesian space is performed taking into account the system geometry, range and azimuth information. Both synthetic and real radar data are used to analyse system operation. During the measurement campaign, a cooperative vehicle was used for validation purposes. Results confirm that ground targets detection and localization are feasible using a single GPS transmitter.

Tree use by koalas after timber harvesting in a mosaic landscape

Context A better understanding of how individual animals use their habitat after disturbance can help optimise management practices for their conservation. Forestry is one such disturbance for koalas that operates under regulations based on best available information to minimise impacts. Aims This study aimed to investigate tree use by koalas in a mosaic of young, regenerating trees after timber harvest and mature trees in adjacent exclusion zones. Methods Tracking collars using very high frequency radio and Global Positioning System transmitters were used to track 10 koalas (five males, five females) across all seasons in three forests, 5–10 years after timber harvesting as regulated by practices current at that time. Tree use was compared to availability based on basal area in different parts of the forest. Key results We tracked koalas to 429 day-trees and 70 night-trees during this time. Males and females displayed little difference in tree use. Blackbutt Eucalyptus pilularis and turpentine Syncarpia glomulifera were the most commonly used species during the day, but blackbutt was ranked with the highest preference relative to tree availability. Tallowwood Eucalyptus microcorys was by far the most commonly used tree at night. Koalas used a broad range of tree sizes during the day and night, but most often used medium-sized trees, with preferences for a diameter of 30–60 cm (slightly smaller at night). Koalas used all topographic positions in the landscape, but more than half of the trees used were in lower topographic areas (gullies and lower slopes). Areas mapped as having previous heavy timber harvesting were the most used forest category, followed by riparian exclusion zones. Conclusions Our results demonstrate that koalas commonly used trees regenerating after harvest, although preferences for medium-sized trees and tallowwood as a night browse tree suggest current forestry regulations can be fine-tuned by retaining a greater proportion of these features. Implications Because most trees were used only once, our results support the view and current practice of retaining habitat patches, such as exclusion zones and wildlife clumps (triggered by a koala habitat model), to provide a mix of species and size classes for both food and shelter. A review of tree size and species retention is recommended.

Dynamic Calibration of GPS Effective Isotropic Radiated Power for GNSS-Reflectometry Earth Remote Sensing

Global Navigation Satellite System (GNSS) Reflectometry uses reflected GNSS signals for Earth remote sensing applications. Absolute calibration of a Delay Doppler Map (DDM) requires an accurate estimate of the effective isotropic radiated power (EIRP) of the GNSS transmitter, e.g., Global Positioning System (GPS). However, variable transmit power by numerous Block II Follow-on (IIF) and II Replenishment-Modernized (IIR-M) GPS space vehicles has been observed due to their flex power mode. Nonuniformity in the GPS antenna gain patterns further complicates EIRP estimation. A dynamic calibration approach is developed to address GPS EIRP variability. It uses measurements by the direct received GPS signal to estimate GPS EIRP in the specular reflected direction and then incorporates it into the calibration of normalized bistatic radar cross section (NBRCS). Error analyses using Monte Carlo simulations and a root sum of squares (RSS) approach show that the resulting error in NBRCS is about 0.32 dB. Dynamic EIRP calibration instantaneously detects and corrects for power fluctuations in the GPS transmitters and significantly reduces errors due to GPS antenna gain azimuthal asymmetry. It allows observations with the most variable Block IIF transmitters (approximately 37% of the GPS constellation) to be included in the standard data products and further improves the calibration quality of NBRCS and geophysical data products.

Breeding Season Space Use by Lesser Prairie-Chickens (Tympanuchus Pallidicinctus) Varies Among Ecoregions and Breeding Stages

Large-scale declines of grassland ecosystems in the conterminous United States since European settlement have led to substantial loss and fragmentation of lesser prairie-chicken (Tympanuchus pallidicinctus) habitat and decreased their occupied range and population numbers by ∼85%. Breeding season space use is an important component of lesser prairie-chicken conservation, because it could affect both local carrying capacity and population dynamics. Previous estimates of breeding season space use are largely limited to one of the four currently occupied ecoregions, but potential extrinsic drivers of breeding space use, such as landscape fragmentation, vegetation structure and composition, and density of anthropogenic structures, can show large spatial variation. Moreover, habitat needs vary greatly among the lekking/prelaying, nesting, brood-rearing, and postbreeding stages of the breeding season, but space use by female lesser prairie-chickens during these stages remain relatively unclear. We tested whether home range area and daily displacement (the net distance between the first and last location of each day) of female lesser prairie-chickens varied among ecoregions and breeding stages at four study sites in Kansas and Colorado, U.S.A., representing three of the four currently occupied ecoregions. We equipped females with very-high-frequency (VHF) or Global Positioning System (GPS) transmitters, and estimated home range area with kernel density estimators or biased random bridge models, respectively. Across all ecoregions, breeding season home range area averaged 190.4 ha (±19.1 ha se) for birds with VHF and 283.6 ha (±23.1 ha) for birds with GPS transmitters, whereas daily displacement averaged 374.8 m (±14.3 m). Average home range area and daily displacement of bird with GPS transmitters were greater in the Short-Grass Prairie/ Conservation Reserve Program Mosaic and Sand Sagebrush Prairie Ecoregions compared to sites in the Mixed-Grass Prairie Ecoregion. Home range area and daily displacement were greatest during lekking/prelaying and smallest during the brood-rearing stage, when female movements were restricted by mobility of chicks. Ecoregion- and breeding stage-specific estimates of space use by lesser prairie-chickens will help managers determine the spatial configuration of breeding stage-specific habitat on the landscape. Furthermore, ecoregion- and breeding stage-specific estimates are crucial when estimating the amount of breeding habitat needed for lesser prairie-chicken populations to persist.

Influence of individual biological traits on GPS fix-loss errors in wild bird tracking

In recent decades, global positioning system (GPS) location data and satellite telemetry systems for data transmission have become fundamental in the study of basic ecological traits in wildlife biology. Evaluating GPS location errors is essential in assessing detailed information about the behaviour of an animal species such as migration, habitat selection, species distribution or foraging strategy. While many studies of the influence of environmental and technical factors on the fix errors of solar-powered GPS transmitters have been published, few studies have focussed on the performance of GPS systems in relation to a species’ biological traits. Here, we evaluate the possible effects of the biological traits of a large raptor on the frequency of lost fixes—the fix-loss rate (FLR). We analysed 95,686 records obtained from 20 Bearded Vultures Gypaetus barbatus tracked with 17 solar-powered satellite transmitters in the Pyrenees (Spain, France and Andorra), between 2006 and 2019 to evaluate the influence of biological, technical, and environmental factors on the fix-loss rate of transmitters. We show that combined effects of technical factors and the biological traits of birds explained 23% of the deviance observed. As expected, the transmitter usage time significantly increased errors in the fix-loss rate, although the flight activity of birds revealed an unexpected trade-off: the greater the proportion of fixes recorded from perched birds, the lower the FLR. This finding seems related with the fact that territorial and breeding birds spend significantly more time flying than non-territorial individuals. The fix success rate is apparently due to the interactions between a complex of factors. Non-territorial adults and subadults, males, and breeding individuals showed a significantly lower FLR than juveniles-immatures females, territorial birds or non-breeding individuals. Animal telemetry tracking studies should include error analyses before reaching any ecological conclusions or hypotheses about spatial distribution.

Pronghorn Winter Resource Selection Before and After Wind Energy Development in South-Central Wyoming

Few studies have evaluated the response of ungulate populations to wind energy development. Recent demand for wind-generated electricity coupled with a tendency for wind-energy facilities to be sited within suitable pronghorn (Antilocapra americana) winter range make this a critical issue for conservation of this icon of western North America. We evaluated pronghorn response to wind energy development at the winter home range scale, as well as within individual winter home ranges using data collected from 47 adult female pronghorn equipped with Global Positioning System transmitters. At both scales, we developed separate resource selection models for pronghorn before (winter 2010) and after (winters 2011 and 2012) development of the Dunlap Ranch wind energy facility in south-central Wyoming to evaluate the potential impacts of wind energy infrastructure on pronghorn winter resource selection. In general, pronghorn winter resource selection was correlated with greater sagebrush (Artemisia spp.) cover, lower snow depth, and lower slopes before and after wind energy development at both scales. At the larger scale, pronghorn selected home ranges closer to wind turbines during all winters. Within home ranges, pronghorn selected areas closer to future locations of wind turbines at Dunlap Ranch during 2010 before turbine erection. However, we found evidence that pronghorn avoided wind turbines in winters after development within their winter home ranges. This relationship was most evident during winter 2011, which coincided with the most severe winter of our study. Long-term replicated studies will be necessary to make inferences for pronghorn populations exposed to wind energy development in different environments and scales than we evaluated. Nonetheless, in the absence of additional information on how ungulates respond to wind energy development, our finding that pronghorn avoided wind turbines within their winter home ranges has important implications for future wind development projects, particularly in areas known to fulfill important seasonal requirements of pronghorn populations.

The Use of SMAP-Reflectometry in Science Applications: Calibration and Capabilities

The Soil Moisture Active Passive (SMAP) mission became one of the newest spaceborne Global Navigation Satellite System–Reflectometry (GNSS-R) missions collecting Global Positioning System (GPS) bistatic radar measurements when the band-pass center frequency of its radar receiver was switched to the GPS L2C band. SMAP-Reflectometry (SMAP-R) brings a set of unique capabilities, such as polarimetry and improved spatial resolution, that allow for the exploration of scientific applications that other GNSS-R missions cannot address. In order to leverage SMAP-R for scientific applications, a calibration must be performed to account for the characteristics of the SMAP radar receiver and each GPS transmitter. In this study, we analyze the unique characteristics of SMAP-R, as compared to other GNSS-R missions, and present a calibration method for the SMAP-R signals that enables the standardized use of these signals by the scientific community. There are two key calibration parameters that need to be corrected: The first is the GPS transmitted power and GPS antenna gain at the incidence angle of the measured reflections and the second is the convolution of the SMAP high gain antenna pattern and the glistening zone (Earth surface area from where GPS signals scatter). To account for the GPS transmitter variability, GPS instrument properties—transmitted power and antenna gain—are collocated with information collected from the CYclone Global Navigation Satellite System (CYGNSS) at SMAP’s range of incidence angles (37.3° to 42.7°). To account for the convolutional effect of the SMAP antenna gain, both the scattering area of the reflected GPS signal and the SMAP antenna footprint are mapped on the surface. We account for the size of the scattering area corresponding to each delay and Doppler bin of the SMAP-R measurements based off the SMAP antenna pattern, and normalize according to the size of a measurement representative to one obtained with an omnidirectional antenna. We have validated these calibration methods through an analysis of the coherency of the reflected signal over an extensive area of old sea ice having constant surface characteristics over a period of 3 months. By selecting a vicarious scattering surface with high coherency, we eliminated scene variability and complexity in order to avoid scene dependent aliases in the calibration. The calibration method reduced the dependence on the GPS transmitter power and gain from ~1.08 dB/dB to a residual error of about −0.2 dB/dB. Results also showed that the calibration method eliminates the effect of the high gain antenna filtering effect, thus reducing errors as high as 10 dB on angles furthest from SMAP’s constant 40° incidence angle.

Target moving trajectory estimation by multiple receivers based on GPS forward scattering radar

The estimation of target moving trajectory by the multiple receivers based on global positioning system (GPS) forward scattering radar has been first presented in the study, which cannot be obtained by the traditional method. A new estimation approach has been considered using the following information. First, the starting and ending time at which the target pass through the baseline of GPS transmitter–receiver can be obtained. Second, the azimuth and elevation angles of GPS satellites are extracted in combination with the satellite sky map at the recording time. On the basis, the target moving trajectory can be obtained by the established model. In order to validate its feasibility, the experiment has been completed in the open area of Beihang University, which regards the human as the target. Four GPS receivers have been employed to record the data. The experimental results show that the estimation of target trajectory is consistent with the real situation, which proves the practical applicability of the proposed technique.

Impact of GPS receiver antenna GRAPHIC residual variations on single-frequency orbit determination of LEO satellites

Single-frequency (SF) precise orbit determination (POD) using space-borne Global Positioning System (GPS) measurements is a prerequisite for the success of many low-cost small/micro low Earth orbit (LEO) satellite missions. The first-order ionospheric effects are usually eliminated by group and phase ionospheric correction (GRAPHIC) combinations. GPS receiver antenna GRAPHIC residual variations (GRVs) are important systematic error sources in SF orbit determination. Azimuth and elevation dependent GRVs are estimated and obtained based on the GRAPHIC combination residuals in an in-flight calibration. One month of data from GRACE-A, GRACE-B, CHAMP and HY-2A satellites is used to assess the potential of receiver antenna GRVs in SF orbit determination. It is the first time to study the impact of receiver antenna GRVs on SF orbit determination for different LEO satellites, which exhibit different altitudes and data qualities. The impact of receiver antenna GRVs on SF orbit determination is significant. The use of in-flight determined receiver antenna GRVs leads to a better consistency between SF and dual-frequency POD solutions. The improvements are more obvious for GRACE-A and CHAMP satellites, whose receiver antenna GRV patterns demonstrate clear characteristics of systematic deviations. After correcting the receiver antenna GRVs, the root-mean-square of satellite laser ranging validation residuals are 3.11 cm, 2.31 cm, 2.86 cm and 5.29 cm for GRACE-A, GRACE-B, CHAMP and HY-2A satellites, respectively, which are reduced by 11.1%, 4.6%, 14.6% and 4.7%, respectively. At last, a set of a priori GDV corrections of GPS transmitter antennas are used in SF orbit determination and its effects on receiver antenna GRVs estimation and SF orbit determination are analyzed. Applying these corrections can slightly improve the SF orbit quality of GRACE-A satellite.

Temporal Stability of GPS Transmitter Group Delay Variations.

The code observable of global navigation satellite systems (GNSS) is influenced by group delay variations (GDV) of transmitter and receiver antennas. For the Global Positioning System (GPS), the variations can sum up to 1 m in the ionosphere-free linear combination and thus can significantly affect precise code applications. The contribution of the GPS transmitters can amount to 0.8 m peak-to-peak over the entire nadir angle range. To verify the assumption of their time-invariance, we determined daily individual satellite GDV for GPS transmitter antennas over a period of more than two years. Dual-frequency observations of globally distributed reference stations and their multipath combination form the basis for our analysis. The resulting GPS GDV are stable on the level of a few centimeters for C1, P2, and for the ionosphere-free linear combination. Our study reveals that the inconsistencies of the GDV of space vehicle number (SVN) 55 with respect to earlier studies are not caused by temporal instabilities, but are rather related to receiver properties.

Spatial Ecology Observations From Feral Horses Equipped With Global Positioning System Transmitters

Spatial Ecology Observations From Feral Horses Equipped With Global Positioning System Transmitters

Intrinsic, environmental, and anthropogenic factors related to pronghorn summer mortality

ABSTRACTPronghorn (Antilocapra americana) are an iconic wildlife species of sagebrush (Artemisia spp.) and grassland ecosystems in western North America. Over 50% of pronghorn have historically occurred in Wyoming; however, these populations have declined by nearly 30% in <2 decades, concurrent with expanding energy development and prolonged drought. Research suggests adult female pronghorn, unlike other temperate ungulates, are more likely to die in summer, when body condition is lower from extreme energetic demands of reproduction, which are higher for pronghorn than other ungulates. To evaluate the potential effects of intrinsic, environmental, and anthropogenic factors on summer mortality risk, we monitored 114 adult female pronghorn equipped with global positioning system transmitters in the Red Desert region of south‐central Wyoming, USA between 2013 and 2015. We modeled mortality risk using Cox's proportional hazards regression. Summer mortality risk was influenced by intrinsic and environmental factors; mortality risk increased when individuals were in poorer body condition entering the previous winter and when they experienced greater variation in average daily snow depth during the previous winter. We did not detect an effect of the distance to and density of roads, oil and gas wells, or fences on pronghorn summer mortality. During years of increased winter severity with deep and fluctuating snow depths, managers may observe higher winter mortality and higher mortality the following summer, likely as a consequence of the energetic expense associated with winter survival and spring reproduction for female pronghorn. © 2018 The Wildlife Society.

Effects of Landscape Characteristics on Annual Survival of Lesser Prairie-Chickens

Abstract Agriculture and development have caused landscape change throughout the southwestern Great Plains in the range of the lesser prairie-chicken (Tympanuchus pallidicinctus). Landscape alteration within the lesser prairie-chicken range may contribute to range contraction and population losses through decreases in survival rates. Our objectives were to determine if: (1) landscape configuration (i.e., the spatial arrangement of habitat) or composition (i.e., the amount of habitat), at the study-site scale, affected annual survival of females, (2) relationships exist between landscape context (i.e., landscape configuration and composition) and weekly survival to assess effects of landscape composition and configuration on lesser prairie-chicken populations, and (3) anthropogenic features influenced daily mortality risk. We captured 170 female lesser prairie-chickens and used very-high-frequency and GPS (Global Positioning System) transmitters to track their movement and survival for 2 y. We used known-f...

Nonbreeding home‐range size and survival of lesser prairie‐chickens

ABSTRACTThe lesser prairie‐chicken (Tympanuchus pallidicinctus), a species of conservation concern with uncertain regulatory status, has experienced population declines over the past century. Most research on lesser prairie‐chickens has focused on the breeding season, with little research conducted during the nonbreeding season, a period that exerts a strong influence on demography in other upland game birds. We trapped lesser prairie‐chickens on leks and marked them with either global positioning system (GPS) satellite or very high frequency (VHF) transmitters to estimate survival and home‐range size during the nonbreeding season. We monitored 119 marked lesser prairie‐chickens in 3 study areas in Kansas, USA, from 16 September to 14 March in 2013, 2014, and 2015. We estimated home‐range size using Brownian Bridge movement models (GPS transmitters) and fixed kernel density estimators (VHF transmitters), and female survival using Kaplan–Meier known‐fate models. Average home‐range size did not differ between sexes. Estimated home‐range size was 3 times greater for individuals fitted with GPS satellite transmitters ( = 997 ha) than those with VHF transmitters ( = 286 ha), likely a result of the temporal resolution of the different transmitters. Home‐range size of GPS‐marked birds increased 2.8 times relative to the breeding season and varied by study area and year. Home‐range size was smaller in the 2013–2014 nonbreeding season ( = 495 ha) than the following 2 nonbreeding seasons ( = 1,290 ha and = 1,158 ha), corresponding with drought conditions of 2013, which were alleviated in following years. Female survival () was high relative to breeding season estimates, and did not differ by study area or year ( = 0.73 ± 0.04 [SE]). Future management could remain focused on the breeding season because nonbreeding survival was 39–44% greater than the previous breeding season; however, considerations of total space needs would benefit lesser prairie‐chickens by accounting for the greater spatial requirements during the nonbreeding season. © 2017 The Wildlife Society.

Apparent survival rates of adult Lesser Spotted Eagle Clanga pomarina estimated by GPS-tracking, colour rings and wing-tags

ABSTRACTCapsule: In the migratory Lesser Spotted Eagle Clanga pomarina, colour rings and Global Positioning System transmitters indicated annual survival rates similar to other large raptors, but the rate suggested by wing-tags was significantly lower due to the higher rate of tag loss.