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Winter survival and resource selection of GPS equipped northern bobwhite in the Rolling Plains of Texas
Abstract
Assessment of northern bobwhite (Colinus virginianus) habitat management practices is often expensive and labor intensive, as is the tracking of bobwhites to measure resource use and reaction to management or experimental treatment. Traditional solutions to both these problems (e.g., aerial and satellite imagery and Very High Frequency tracking tags [VHF]) each have issues including lengthy return times, coarse scale, high labor inputs, and possible observer bias. Northern bobwhite researchers have recently begun to use solar powered Global Positioning System tags (GPS) to acquire fine scale northern bobwhite location data. I first compared differences in daily survival probabilities between northern bobwhite wearing typical VHF tags and GPS tags in the Rolling Plains of Texas from 2017 – 2019. I estimated apparent survival for northern bobwhites (n = 112) during the non-breeding season, 1 October – 31 March. When possible, I paired northern bobwhites of similar mass in the same coveys with both transmitter types and used radio telemetry to determine fates of radio-tagged northern bobwhites. I developed 3 a priori models using the nest survival model in Program MARK to estimate daily survival probabilities (DSP) for both transmitter pairings as well as to explore the relationship between survival and quail mass. Northern bobwhites fitted with GPS backpacks had 0.03 lower daily survival probabilities compared to VHF necklace-equipped northern bobwhites with non-overlapping 95% confidence intervals (GPS DSP = 0.95; SE = 0.008; VHF DSP = 0.98; SE = 0.003).
Next, I evaluated the efficacy of using an Unmanned Aerial Vehicle (UAV) paired with GPS tag data to assess northern bobwhite habitat. I used an UAV to collect high resolution georeferenced imagery of the home ranges of a subset of my study animals (n = 20). These images were developed into a Land Use Land Cover map to quantify the cover found in the home ranges of those northern bobwhite and to estimate their resource selection based on the data collected from the GPS tags. I was able to classify northern bobwhite cover into typical canopy classes (bare, shrub, grass; mean overall accuracy = 91.47% ± 2.57; mean Kappa = 0.88 ± 0.03). I observed no significant 2nd or 3rd order habitat selection during the first winter. In the second winter I observed selection for shrubs (Wi = 1.1 ± 0.64) and against grasses (Wi = 0.59 ± 0.21). My results suggest caution is warranted in selection of new sensor and harness pairings, and that while solar GPS tags may not affect movement-based questions, their use may bias survival related questions. Additionally, UAVs may fit a needed role in timely data collection, but their use should be matched with the appropriate spatial and temporal scale needed to answer the specific research question.
... Bobwhite were relocated 5-7 days/week using Biotracker receivers and 3-element directional antennae from Lotek Wireless Inc. (Newmarket, Ontario, Canada) via homing telemetry (White andGarrott 1990, Amelon et al. 2009). Locations were taken approximately 20-30 m from individual bobwhites at varying times of the day to minimize disturbance and account for possible variation in diurnal resource selection. ...
... For example, a researcher's presence may affect the animal's natural movements and introduce biases in estimates of habitat utilization. Additionally, adverse terrain and researcher errors may negatively affect VHF telemetry precision and accuracy (White andGarrott 1990, Fuller et al. 2005). Researchers have deployed Global Positioning Systems (GPS) equipment to monitor animal movements (Steiner et al. 2000, Hulbert and French 2001, Phillips et al. 2003. ...
... These 2 extra grams could add too much weight to the units during certain times of the year when bobwhite weigh less (i.e., winter months) and could cause units to exceed the <5% body weight threshold that is recommended for telemetry units attached to wildlife (Caccamise and Hedin 1985, Aldridge and Bringham 1988, Bridge et al. 2011. White (2021) observed that bobwhite equipped with a ~8.5 g solar GPS and VHF backpack had a significantly lower daily survival probability than bobwhite wearing traditional 6 g necklace-style VHF transmitters. However, the author was unable to establish a positive linear relationship between increasing bobwhite mass and daily survival probabilities and suggested that the maximum tolerable mass may be lower for backpack configurations (White 2021). ...
... For example, a researcher's presence may affect the animal's natural movements and introduce biases in estimates of habitat utilization. Additionally, adverse terrain and researcher errors may negatively affect VHF telemetry precision and accuracy (White andGarrott 1990, Fuller et al. 2005). Researchers have deployed Global Positioning Systems (GPS) equipment to monitor animal movements (Steiner et al. 2000, Hulbert and French 2001, Phillips et al. 2003. ...
... These 2 extra grams could add too much weight to the units during certain times of the year when bobwhite weigh less (i.e., winter months) and could cause units to exceed the <5% body weight threshold that is recommended for telemetry units attached to wildlife (Caccamise and Hedin 1985, Aldridge and Bringham 1988, Bridge et al. 2011. White (2021) observed that bobwhite equipped with a ~8.5 g solar GPS and VHF backpack had a significantly lower daily survival probability than bobwhite wearing traditional 6 g necklace-style VHF transmitters. However, the author was unable to establish a positive linear relationship between increasing bobwhite mass and daily survival probabilities and suggested that the maximum tolerable mass may be lower for backpack configurations (White 2021). ...
... White (2021) observed that bobwhite equipped with a ~8.5 g solar GPS and VHF backpack had a significantly lower daily survival probability than bobwhite wearing traditional 6 g necklace-style VHF transmitters. However, the author was unable to establish a positive linear relationship between increasing bobwhite mass and daily survival probabilities and suggested that the maximum tolerable mass may be lower for backpack configurations (White 2021). Since we began our research, however, technological advances have decreased the weight of VHF (<1.0 g) and micro-GPS (4.5 g) transmitters considerably, which could make this consideration a moot point. ...
The use of Global Positioning Systems (GPS) transmitters on northern bobwhite (Colinus virginianus; hereafter, bobwhite) could increase our understanding of fine-scale movements and habitat use for a declining game bird species. We evaluated solar-recharged micro-GPS dataloggers to determine the effectiveness of the units on free-ranging bobwhite and we conducted a controlled experiment to determine the accuracy of the dataloggers under a variety of canopy cover. We deployed the micro-GPS dataloggers on 25 bobwhites between August 2016 and April 2017 across 4 different ranches in the Rolling Plains of West Texas, USA. Accuracy (± standard error) for the 8 dataloggers across 3 trials for the stationary tests was 25.4 ± 3.8 m. Daily movement of bobwhite averaged 0.96 ± 0.09 km and morning movements averaged 0.49 ± 0.07 km. Average 95% and 50% minimum convex polygons for bobwhite area utilization were 15.2 ha and 3.6 ha, respectively. Our data indicate that solar-recharged micro-GPS dataloggers can be used to monitor bobwhites’ short-term fine-scale movements in West Texas.
Drones are increasingly popular tools for wildlife research, but it is importantthat the use of these tools does not overshadow reporting of methodological detailsrequired for evaluation of study designs. Thediversity in drone platforms, sensors, andapplications necessitates the reporting of specific details for replication, but there is littleguidance available on how to detail drone use in peer-reviewed articles. Here, we presenta standardized protocol to assist researchers in reporting of their drone use in wildliferesearch. The protocol is delivered in six sections: Project Overview; Drone System andOperation Details; Payload, Sensor, and DataCollection; Field Operation Details; DataPost-Processing; and Permits, Regulations, Training, and Logistics. Each section outlinesthe details that should be included, along with justifications for their inclusion. To facilitateease of use, we have provided two example protocols, retroactively produced for publisheddrone-based studies by the authors of this protocol. Our hopes are that the current versionof this protocol should assist with the communication, dissemination, and adoption ofdrone technology for wildlife research and management.
Backpack-mounted satellite transmitters (PTTs) are used extensively in the study of avian habitat use and of the movements and demography of medium- to large-bodied species, but can affect individuals’ performance and fitness. Transparent assessment of potential transmitter effects is important for both ethical accountability and confidence in, or adjustment to, life history parameter estimates. We assessed the influence of transmitters on seven reproductive parameters in Asian houbara Chlamydotis macqueenii, comparing 114 nests of 38 females carrying PTTs to 184 nests of untagged birds (non-PTT) over seven breeding seasons (2012–2018) in Uzbekistan. There was no evidence of any influence of PTTs on: lay date (non-PTT x̅ = 91.7 Julian day ± 12.3 SD; PTT x̅ = 95.1 Julian day ± 15.7 SD); clutch size (non-PTT x̅ = 3.30 ± 0.68 SD; PTT x̅ = 3.25 ± 0.65 SD); mean egg weight at laying (non-PTT x̅ = 66.1 g ± 5.4 SD; PTT x̅ = 66.4 g ± 5.4 SD); nest success (non-PTT x̅ = 57.08% ± 4.3 SE; PTT x̅ = 58.24% ± 4.5 SE for nests started 2 April); egg hatchability (non-PTT x̅ = 88.3% ± 2.2 SE; PTT x̅ = 88.3% ± 2.6 SE); or chick survival to fledging from broods that had at least one surviving chick (non-PTT x̅ = 63.4% ± 4.2 SE; PTT x̅ = 64.4% ± 4.7 SE). High nesting propensity (97.3% year⁻¹ ± 1.9% SE) of tagged birds indicated minimal PTT effect on breeding probability. These findings show that harness-mounted transmitters can give unbiased measures of demographic parameters of this species, and are relevant to other large-bodied, cursorial, ground-nesting birds of open habitats, particularly other bustards.
Reliable demographic estimates hinge on the assumption that marking animals does not alter their behavior, reproduction , or survival. Violations can bias inference and are especially egregious for species of high conservation concern. Global positioning system (GPS) devices represent a recent technological advancement that has contributed greatly to avian ecological studies compared with traditionally used very high frequency (VHF) radio transmitters, but may affect demographic rates differently than VHF transmitters. We compared survival between VHF (necklace attachment) and GPS (rump-mounted attachment) devices from >1,100 Greater Sage-Grouse (Centrocercus urophasianus), a species of high conservation concern, across multiple populations within California and Nevada. We found lower survival for GPS-marked compared to VHF-marked sage-grouse across most sex, age, and seasonal comparisons. Estimates of annual survival for GPS-marked sage-grouse were 0.55-0.86 times that of VHF-marked birds with considerable variation among sex and age classes. Differences in survival could be attributed to features associated with GPS devices, including greater weight, position of attachment (e.g., rump-mount harness), and a semi-reflective solar panel. In a post hoc analysis, we evaluated additive and interactive effects between device type (GPS vs. VHF) and transmitter mass as a proportion of body mass (PBM). While the device type effect alone was the best model, the PBM interaction also had support. For GPS devices, survival decreased with increasing PBM, whereas PBM effects were not found for VHF. We attributed differences in PBM effect to placement of transmitters on sage-grouse, as weight of GPS devices was positioned rearward. This information can help managers and researchers weigh costs and benefits of GPS-based monitoring. Our results indicate demographic data collected from GPS devices should be interpreted with caution, and use of these devices should be tailored to specific ecological questions. Future research aimed at investigating behavioral impacts and GPS designs that reduce adverse impacts on survival would be beneficial. Los dispositivos de seguimiento de los sistemas de posicionamiento global pueden disminuir la supervivencia de Centrocercus urophasianus RESUMEN Las estimaciones demográficas confiables se basan en el supuesto de que la marcación de los animales no altera su comportamiento, reproducción o supervivencia. La violación de estos supuestos puede sesgar las inferencias y son especialmente preocupantes para especies de alto valor de conservación. Los dispositivos de los sistemas de posicionamiento global (GPS por sus siglas en inglés) representan un avance tecnológico reciente que ha contribuido enormemente en los estudios de ecología de aves en comparación con los radio-transmisores de muy alta frecuencia (VHF por sus siglas en inglés) usados tradicionalmente, pero pueden afectar las tasas demográficas de modo diferentes a los transmisores VHF. Comparamos la supervivencia entre dispositivos VHF (agarrados al cuello) y GPS (agarrados a la rabadilla) de >1100 individuos de Centrocercus urophasianus, una especie de alto valor de conservación, a lo largo de múltiples poblaciones en California y Nevada. Encontramos menor supervivencia de individuos marcados con GPS en comparación con individuos marcados con VHF para la mayoría de las comparaciones de sexos, edades y estaciones. Las estimaciones de supervivencia anual de los individuos marcados con GPS fueron 0.55-0.86 veces que la de los individuos marcados con VHF con variaciones considerables entre sexos y clases de edad. Las diferencias en supervivencia podrían atribuirse a características asociadas con los dispositivos GPS, incluyendo mayor peso, posición de agarre (e.g., arnés montado en la rabadilla) y panel solar semi-reflectante. En un análisis post hoc, evaluamos los efectos aditivos e interactivos entre los tipos de dispositivo (GPS vs. VHF) y el peso de los transmisores como una proporción de la masa corporal (PMC). Mientras que el efecto del tipo de dispositivo representó el mejor modelo, la interacción de la PMC también obtuvo apoyo. Para los dispositivos GPS, la supervivencia disminuyó con un aumento de la PMC, mientras que no se encontraron efectos de la PMC para VHF. Atribuimos las diferencias en el efecto de la PMC al emplazamiento de los transmisores en los individuos, ya que el peso de los dispositivos GPS se ubicó en la parte trasera. Esta información puede ayudar a los gestores e investigadores a sopesar los costos y beneficios del monitoreo con GPS. Nuestros resultados in-dican que los datos demográficos colectados con dispositivos GPS deberían ser interpretados con cuidado, y el uso de estos dispositivos debería estar vinculado a preguntas ecológicas específicas. Serían beneficiosas investigaciones futuras dirigidas a estudiar los efectos en el comportamiento y los diseños de GPS que reduzcan los impactos adversos en la supervivencia.
Avian biologists routinely estimate sampling variance for parameter estimates such as daily nest survival, fecundity, annual survival, and density. However, many biologists are not certain of methods to derive sampling variance for parameters when survival rates change temporal scales. Similar methods are needed to obtain sampling variance when biologists combine parameter estimates to calculate an indirect demographic parameter, such as population growth rate. The delta method is a useful technique for approximating sampling variance when the desired demographic parameter is a function of at least one other demographic parameter. However, the delta method is rarely taught in most graduate-level biology or ecology courses, and application of this method may be discouraged by seemingly daunting formulas in reference books. Here, I provide five examples of sampling variance approximations for common situations encountered by avian ecologists, with step-by-step explanations of the equations involved.
Understanding the impact of radiomarking northern bobwhite (Colinus virginianus) survival is essential because of the widespread reliance on radiotelemetry to assess vital population parameters. We conducted an assessment of bobwhite populations within the Central Hardwoods Bird Conservation Region using leg banding and radiotelemetry on Peabody Wildlife Management Area, a 3,330-ha reclaimed surface mine in western Kentucky. We captured bobwhites using baited funnel traps during a 112-day period (23 Jul-11 Nov 2010) and marked 180 with necklace-style radio-transmitters (6 g) and 256 birds with only leg bands. Eighty-five birds were opportunistically recaptured in funnel traps, of which 81 were used in developing survival estimates. We used the Cormack-Jolly-Seber model in Program MARK to estimate periodic survival rates (PSR) of both sample groups. Candidate models which included body mass as a covariate explained the most variability in survival. The estimated PSR was 0.309 6 0.109 based on the best approximating model and was 0.302 6 0.108 from model averaging. We calculated a point of inflection for this model, which suggested a mass 'threshold' of 131g, above which survival improved at a decreasing rate. The model including only the radio-transmitter effect had a DAIC c .3 and was considered to be non-plausible. Further research with larger samples is needed to develop more robust survival models to fully assess the effects of radiomarking bobwhites. It does not appear, based on our study, that radio transmitters adversely affect survival of northern bobwhite.. 2012. Survival of radio-marked versus leg-banded northern bobwhite in Kentucky.
Understanding patterns in the spatial distribution of individuals in a population is a central question in ecology. Concurrent with advances in biotelemetry devices, development of home range estimator methods incorporating the temporal component of locational fixes are increasingly used to investigate these patterns at finer scales. However, these methods may necessitate sampling schedules that limit battery life and study period length. Practically, evaluating how home range estimator methods affect calculations of space use and habitat selection prior to deployment of biotelemetry devices could help researchers optimize data acquisition schedules. We quantified spatial overlap between a home range estimator using temporal information (dynamic Brownian bridge movement model [dBBMM]) and home range estimators not incorporating the temporal component of fixes (ad hoc and href kernel density estimator [KDE]) across differing sample schedules, and the resulting error in habitat selection ratios using data collected from wild turkeys (Meleagris gallopavo) equipped with Global Positioning Systems units in Texas, Georgia, South Carolina, and Louisiana, USA, during February–May 2015. When comparing ranges created from KDEs to dBBMM, commission errors were large (20–80%) and did not diminish with increased sampling rates. In contrast, omission error rate declined quicker and improvements were minimal when fix rates increased beyond 4/day. Compared with ranges estimated with dBBMM, KDEs poorly defined the spatial bearings of an individual's range, overestimated areas of use, underestimated areas avoided, and showed different patterns of habitat selection. Our results suggest home range estimator methods incorporating temporal information seem capable of estimating ranges encompassing nearly all area used by an individual and should be used even at relatively low-frequency collection schedules to assess home ranges of wild turkeys. If researchers are interested in describing habitat selection of wild turkeys, we recommend a sampling schedule of ≤1 location/hour during daytime and dBBMM for range estimation. © 2018 The Wildlife Society.
Modern ecological research often involves the comparison of the usage of habitat types or food items to the availability of those resources to the animal. Widely used methods of determining preference from measurements of usage and availability depend critically on the array of components that the researcher, often with a degree of arbitrariness, deems available to the animal. This paper proposes a new method, based on ranks of components by usage and by availability. A virtue of the rank procedure is that it provides comparable results whether a questionable component is included or excluded from consideration. Statistical tests of significance are given for the method. The paper also offers a hierarchical ordering of selection processes. This hierarchy resolves certain inconsistencies among studies of selection and is compatible with the analytic technique offered in this paper.
The North American Breeding Bird Survey is a roadside, count-based survey conducted by volunteer observers. Begun in 1966, it now is a primary source of information on spatial and temporal patterns of population change for North American birds. We analyze population change for states, provinces, Bird Conservation Regions, and the entire survey within the contiguous United States and southern Canada for 426 species using a hierarchical log-linear model that controls for observer effects in counting. We also map relative abundance and population change for each species using a spatial smoothing of data at the scale of survey routes. We present results in accounts that describe major breeding habitats, migratory status, conservation status, and population trends for each species at several geographic scales. We also present composite results for groups of species categorized by habitats and migratory status. The survey varies greatly among species in percentage of species' range covered and precision of results, but consistent patterns of decline occur among eastern forest, grassland, and aridland obligate birds while generalist bird species are increasing.
The validity of radio-telemetry to produce reliable information (e.g., survival estimates) has recently been chal-lenged. Radio-telemetry is a widely used technique in studies of numerous species, therefore, concerns re-garding potential bias in these estimates warrant further investigation. As such, and as part of a larger study, we investigated 3 aspects of potential radio-bias: 1) variation in survival distributions among treatment (newly radio-tagged) and control (previously radio-tagged) groups; 2) proportion of trapped animals censored during the traditional 7-day censor period; and 3) ramifications to cause-specific mortality through estimation of har-vest rate. Kaplan-Meier survival, based on 30-day post trapping, was similar between treatment (n = 901) and control (n = 293) bobwhites for all but 1 of 8 trapping sessions during 2000-2004. In this case, treatment bob-whites (0.970, SE = 0.015) had higher survival than control birds (0.878, SE = 0.042). We determined the effect of censoring relative to sample size was inconsequential for our analysis because the proportion of bobwhites (18 out of 1,350; 0.013) meeting the criteria for censoring, i.e., dying during the first 7 days, was minimal. Cen-soring of these data influenced survival estimates by an average of only 0.016 (SE = 0.004; range: 0.00 -0.04). We evaluated harvest rate by comparing first year recovery rates of banded verses radio-tagged birds during thirteen hunting seasons occurring between 1992 and 2005. Annual recovery rate was not different (P < 0.05) for banded birds and radio-tagged birds where harvest averaged 6.68% (range 3.3 -11.7) and 6.65% (range 3.4 -11.1), respectively. These findings are consistent with previous research demonstrating that radio-telemetry can provide reliable demographic information. However, we recommend that future researchers test for these potential effects among their data before making biological inferences.
Externally mounted transmitters or loggers may adversely affect migration performance for reasons other than the effects of added mass. The added frontal area of a payload box increases drag, and if the box triggers separation of the boundary layer over the posterior body, the drag coefficient could also be increased, possibly by a large amount. Any such effects would lead directly to a decreased migration range and reduced energy reserves on completion of migration. We measured the body drag coefficients of Rose-coloured Starlings in the Seewiesen wind tunnel by the wingbeat-frequency method. The speed at which the wingbeat frequency passed through a minimum was taken to be an estimate of the minimum-power speed (V
mp), from which the body drag coefficient was calculated in turn. Dummy transmitter boxes were mounted on the bird’s back by attaching them with Velcro to a side-loop harness pad. The pad alone projected 6 mm above the bird’s back, and increased the drag coefficient by nearly 50%, as compared to the “clean” configuration with no harness. Adding boxes (square-ended or streamlined) produced no further significant increase in the drag coefficient, but the addition of a sloping antenna increased it to nearly twice the clean value. These increases are attributed to separation of the boundary layer over the posterior upper body, triggered by the payload. We then ran computer simulations of a particular Barnacle Goose, for which detailed information was available from an earlier satellite-tracking project, to see how its migration range and reserves on arrival would be affected if its transmitter installation also caused flow separation and affected the body drag coefficient in a similar way. By representing the range calculation in terms of energy height, we separated the effect of the transmitter’s mass, which reduces the fat fraction (and hence also energy height) at departure, from that of flow separation, which steepens the energy gradient. The effect of the mass is small, and increases only slightly with increasing distance, whereas a steeper energy gradient not only reduces the range but also reduces the reserves remaining on arrival, to an extent that increases with migration distance. Energy height is related to the fat fraction rather than the fat mass, and is therefore preferable to energy as such, for expressing reserves in birds of different sizes.
Estimation of avian nest survival has traditionally involved simple measures of apparent nest survival or Mayfield constant-nest-survival models. However, these meth- ods do not allow researchers to build models that rigorously assess the importance of a wide range of biological factors that affect nest survival. Models that incorporate greater detail, such as temporal variation in nest survival and covariates representative of individual nests represent a substantial improvement over traditional estimation methods. In an attempt to improve nest survival estimation procedures, we introduce the nest survival model now available in the program MARK and demonstrate its use on a nesting study of Mountain Plovers (Charadrius montanusTownsend) in Montana, USA. We modeled the daily survival of Mountain Plover nests as a function of the sex of the incubating adult, nest age, year, linear and quadratic time trends, and two weather covariates (maximum daily temperature and daily precipitation) during a six-year study (1995-2000). We found no evidence for yearly differences or an effect of maximum daily temperature on the daily nest survival of Mountain Plovers. Survival rates of nests tended by female and male plovers differed (female rate 5 0.33; male rate 5 0.49). The estimate of the additive effect for males on nest survival rate was 0.37 (95% confidence limits were 0.03, 0.71) on a logit scale. Daily survival rates of nests increased with nest age; the estimate of daily nest-age change in survival in the best model was 0.06 (95% confidence limits were 0.04, 0.09) on a logit scale. Daily precipitation decreased the probability that the nest would survive to the next day; the estimate of the additive effect of daily precipitation on the nest survival rate was 21.08 (95% confidence limits were 22.12, 20.13) on a logit scale. Our approach to modeling daily nest-survival rates allowed several biological factors of interest to be easily included in nest survival models and allowed us to generate more biologically meaningful estimates of nest survival.
Northern bobwhites (Colinus virginianus) have captured the public's interest for many years. Part of this interest can be attributed to the favorable impact that bobwhite hunting has on local economies. Landowners can supplement their income via fee-lease hunting, while local merchants benefi t from the increased business caused by the infl ux of hunters. Interest in bobwhites, however, does not accrue solely from a consumptive perspective. These birds also are popular in the nonconsumptive realm among photographers, artists, and birders. Copyright © 2007 by Leonard Alfred Brennan Manufactured in the United States of America All rights reserved.
1. Researchers often attach transmitters and other devices to free-living birds without a clear understanding of potential deleterious consequences to their study organisms, and thus to their data. Studies investigating this topic have generally been limited to a single species or type of device.
2. To achieve a broader understanding we used a meta-analysis of 84 studies to ask: (1) Do devices have an overall effect on birds? (2) Which aspects of avian behaviour and ecology are affected? (3) What attributes of birds influence transmitter effects? (4) What attributes of devices influence their effects? (5) Are effects partially a consequence of capture and restraint?
3. We found a significant negative effect of devices on birds, both overall and for 8 of the 12 specific aspects analysed. The most substantial effects were that birds with devices had markedly increased energy expenditure and were much less likely to nest.
4. Effects were independent of attributes of the birds (sex, age, primary method of locomotion and body mass). We also found no evidence that proportionally heavier devices had greater effects, although researchers generally avoided using heavy devices. Breast-mounted and harness attachments increased device-induced behaviours such as preening, however, and the risk of device-induced mortality differed between attachment methods.
5. Other than foraging behaviours, no effects were a consequence of capture or restraint.
6.Synthesis and applications. We provide the first comprehensive evidence that transmitters and other devices negatively affect birds and may bias resulting data. Researchers should balance the benefits of using these techniques against potential costs to the birds and reliability of the data obtained.
The practical analysis of space use and habitat selection by animals is often a problem due to the lack of well-designed programs. I present here the “adehabitat” package for the R software, which offers basic GIS (Geographic Information System) functions, methods to analyze radio-tracking data and habitat selection by wildlife, and interfaces with other R packages. These tools can be downloaded freely on the internet. Because the functions of this package can be combined with other functions of R, “adehabitat” provides a powerful environment for the analysis of the space and habitat use.
1. The recently developed Brownian bridge movement model (BBMM) has advantages over traditional methods because it quantifes the utilization distribution of an animal based on its movement path rather than individual points and accounts for temporal autocorrelation and high data volumes. However, the BBMM presumes unrealistic homogeneous movement behaviour across all data.
2. Accurate quantification of the utilization distribution is important for identifying the way animals use the landscape.
3. We improve the BBMM by allowing for changes in behaviour, using likelihood statistics to determine change points along the animal's movement path.
4. This novel extension, outperforms the current BBMM as indicated by simulations and examples of a territorial mammal and a migratory bird. The unique ability of our model to work with tracks that are not sampled regularly is especially important for GPS tags that have frequent failed fixes or dynamic sampling schedules. Moreover, our model extension provides a useful one dimensional measure of behavioural change along animal tracks.
5. This new method provides a more accurate utilization distribution that better describes the space use of realistic, behaviourally heterogeneous tracks.
Although the home range is a fundamental ecological concept, there is considerable debate over how it is best measured. There is a substantial literature concerning the precision and accuracy of all commonly used home range estimation methods; however, there has been considerably less work concerning how estimates vary with sampling regime, and how this affects statistical inferences.
We propose a new procedure, based on a variance components analysis using generalized mixed effects models to examine how estimates vary with sampling regime.
To demonstrate the method we analyse data from one study of 32 individually marked roe deer and another study of 21 individually marked kestrels. We subsampled these data to simulate increasingly less intense sampling regimes, and compared the performance of two kernel density estimation (KDE) methods, of the minimum convex polygon (MCP) and of the bivariate ellipse methods.
Variation between individuals and study areas contributed most to the total variance in home range size. Contrary to recent concerns over reliability, both KDE methods were remarkably efficient, robust and unbiased: 10 fixes per month, if collected over a standardized number of days, were sufficient for accurate estimates of home range size. However, the commonly used 95% isopleth should be avoided; we recommend using isopleths between 90 and 50%.
Using the same number of fixes does not guarantee unbiased home range estimates: statistical inferences differ with the number of days sampled, even if using KDE methods.
The MCP method was highly inefficient and results were subject to considerable and unpredictable biases. The bivariate ellipse was not the most reliable method at low sample sizes.
We conclude that effort should be directed at marking more individuals monitored over long periods at the expense of the sampling rate per individual. Statistical results are reliable only if the whole sampling regime is standardized. We derive practical guidelines for field studies and data analysis.
Measuring percent occurrence of objects from digital images can save time and expense relative to conventional field measurements. However, the accuracy of image analysis had, until now, not reached the level of the best conventional field measurements. Additionally, most image-analysis software programs require advanced user training to successfully analyze images. Here we present a new software program, 'SamplePoint,' that provides the user a single-pixel sample point and the ability to view and identify the pixel context. We found SamplePoint to allow accuracy comparable with the most accurate field-methods for ground-cover measurements. Expert use of the program requires minimal training and its ease of use allows rapid measurements from image data. We recommend SamplePoint for calibrating the threshold-detection level of image-analysis software or for making direct measurements of percent occurrence from digital images.
In Texas, mesquite and yellow-bluestem invasions are widespread. Identifying and monitoring juvenile and adult plants using high-resolution imagery from airborne sensors while they colonize new areas across the landscape can help land managers prioritize locations for treatment and eradication. In this study, we evaluated how data collection design using an unmanned aerial system (UAS) can affect plant detection and mapping. We used a Phantom 3 Professional unmanned aerial vehicle with a Parrot Sequoia multispectral camera for detecting and mapping native honey mesquite (Prosopis glandulosa) and non-native yellow bluestem (Bothriochloa ischaemum) at a rangeland site in northwest Texas. Flights were conducted seasonally during the period from summer 2017 to fall 2018 to test the seasonal impact of detecting plant species. Flights were conducted at altitudes of 30, 60, and 100 m, and four image classification techniques were tested to determine their viability of detecting distinct plant species. Results suggest that flights at 100-m aircraft altitude during the spring season are more effective (>80% user accuracies) for mapping mesquite canopies based on reflectance values and image segmentation information. Yellow bluestem mapping accuracies were low (< 20% user accuracies). Lower spatial resolution (100-m altitude flights, 12-cm pixel resolution) provided less noise and more generalization capabilities for the image classification methods. Overall, random forests and Support Vector Machine classification algorithms outperformed probability-based image classifiers. Land owners and rangeland ecologists using their own UAS in rangeland management can use this information to plan their data collection campaigns before the application of chemical treatments or manual eradication.
The kappa coefficient is not an index of accuracy, indeed it is not an index of overall agreement but one of agreement beyond chance. Chance agreement is, however, irrelevant in an accuracy assessment and is anyway inappropriately modelled in the calculation of a kappa coefficient for typical remote sensing applications. The magnitude of a kappa coefficient is also difficult to interpret. Values that span the full range of widely used interpretation scales, indicating a level of agreement that equates to that estimated to arise from chance alone all the way through to almost perfect agreement, can be obtained from classifications that satisfy demanding accuracy targets (e.g. for a classification with overall accuracy of 95% the range of possible values of the kappa coefficient is −0.026 to 0.900). Comparisons of kappa coefficients are particularly challenging if the classes vary in their abundance (i.e. prevalence) as the magnitude of a kappa coefficient reflects not only agreement in labelling but also properties of the populations under study. It is shown that all of the arguments put forward for the use of the kappa coefficient in accuracy assessment are flawed and/or irrelevant as they apply equally to other, sometimes easier to calculate, measures of accuracy. Calls for the kappa coefficient to be abandoned from accuracy assessments should finally be heeded and researchers are encouraged to provide a set of simple measures and associated outputs such as estimates of per-class accuracy and the confusion matrix when assessing and comparing classification accuracy.
Montezuma quail ( Cyrtonyx montezumae ) occur throughout the desert mountain ranges in the Trans-Pecos of Texas as well as Arizona, New Mexico, and Mexico. Limited information on life history and ecology of the species is available due to the cryptic nature of the bird. Home range, movements, and preferred habitats have been speculated upon in previous literature with the use of observational or anecdotal data. We used innovative trapping techniques and technologically advanced radio transmitters to assess these ecological parameters for Montezuma quail. The goal of this study was to monitor Montezuma quail to determine home range size, movements, and habitat preference for the Davis Mountains population. We captured a total of 72 birds over the course of two years (2009 – 2010) (36M, 35F, 1 Undetermined). Thirteen individuals with >25 locations/bird were used to estimate the home range, movement, and habitat selection analyses. Home ranges (95% kernel density estimators) averaged 12.83 ha and varied greatly (0.02 – 43.29 ha). Maximum straight-line distances between known locations within home ranges varied from 0.73 – 14.83 km. Distances of movements were greater than previously reported. Preferred habitats consisted of Canyon Mountain Savannah and Foothill Slope Mountain Savannah across three spatial scales. Although our study was able to address some basic ecological attributes of Montezuma quail, additional research is warranted to better understand their population dynamics.
Authored by some of the state's top wildlife scientists, The Upland and Webless Migratory Game Birds of Texas presents the most up-to-date and comprehensive reference information covering twenty-one species of game birds. Ranging from the most well-known, like the Wild Turkey and Mourning Dove, to the marsh-loving rails and other more elusive species, these birds have widespread appeal among both hunters and birders and underscore the diverse challenges facing wildlife scientists, land managers, and conservationists in Texas today. From cultural significance to taxonomy and evolutionary history, this volume provides a wealth of background information on these species. Additionally, the book offers illustrated species accounts, detailed range maps, and information about habitat and management requirements, hunting regulations, and research priorities. Readers will gain a deeper understanding of these game birds and the array of terrestrial and wetland landscapes key to their survival. This will serve as a convenient and thorough reference volume for wildlife biologists and enthusiasts, as well as landowners and hunters.
The Rolling Plains have historically provided some of the best opportunities to hunt northern bobwhite (Colinus virginianus) populations anywhere. Historically, scaled quail (Callipepla squamata) have been common to abundant over much of the Rolling Plains, but the populations decreased dramatically in the late 1980s and have been slow to reclaim their historic range. Copyright © 2007 by Leonard Alfred Brennan Manufactured in the United States of America All rights reserved.
Declines in northern bobwhite (Colinus virginianus) populations have led landowners in Texas, USA, to develop various management strategies to combat waning abundance. One common management strategy is to provide supplemental feed to bobwhites, despite the paucity of information regarding the effects of supplemental feed on bobwhite space use and survival. We examined survival and home range of bobwhites using the technique of spreading supplemental feed into roadside vegetation in the Texas Rolling Plains. The study sites were divided into 8 (404.6-ha) units randomly designated as treatment (feed provided) or control (feed withheld). Treatment and control units were rotated during the second field season to minimize potential habitat bias. Treatment units received approximately 69.1 kg/km of milo (Sorghum bicolor) twice per month. We captured and radiomarked 197 female bobwhites (82 treatment [48: 2010–2011; 34: 2011–2012], 115 control [64: 2010–2011; 51: 2011–2012]) from autumn 2010 to spring 2012. Females were monitored for location and survival with radiotelemetry 3–4 times/week. Average home-range size was similar on control and treatment units (47.6 ha [8.7 SE] and 46.2 ha [10.3 SE], respectively). We estimated survival rate with the nest survival model in Program MARK. We observed an increase in survival rate on treatment units compared with control units, regardless of year or environmental conditions. Our results suggest that distributing supplemental feed into roadside vegetation positively influences bobwhite survival with no reduction in home range size. © 2015 The Wildlife Society.
To better understand the reproductive mechanisms that enable northern bobwhite (Colinus virginianus) to recover from high annual mortality, we studied the reproductive strategies, success, and mating systems of 321 radio-marked bobwhite in northern Missouri during 1990-92. Seventy-four female and 43 male bobwhite incubated 159 nests. Females exhibited apparent monogamy during 60% of nesting attempts and apparent polyandry during 40%. Over the entire nesting season, 71% of females were polyandrous. Of those birds alive 15 April (n = 112 F, n = 148 M), 40.2% of females and 13.5% of males successfully hatched ≥1 nest. Seventy-four percent of females (n = 42) and 26% of males (n = 50) surviving until 1 September successfully hatched ≥1 nest. Nesting females that survived the nesting period incubated a mean of 1.8 nests (SE = 0.13), and males incubated 1.0 nests (SE = 0.04). Of those birds that failed on an initial nesting attempt, 57.9% of females (n = 38) and 2 of 23 males incubated ≥1 renest. Of those females that were successful on their initial nesting attempt, 25.7% attempted second nests. Female first nests represented 45.9%, female renests 20.1%, female double-clutch attempts 5.7%, and male-incubated nests 28.3% of all nests located. Nest survival was 43.7% (SE = 3.9). The reproductive system of northern bobwhite enables recovery from low annual survival or periodic catastrophic declines and may be an adaptation to fluctuating resources in ephemeral, dynamic habitats.
We recorded recovery rates for 300 adult female ring-necked pheasants (Phasianus colchicus) and 150 juveniles (82 M, 68 F) marked with 2 different dummy radio tags or leg bands. Birds with backpack tags in all age and sex categories disappeared more quickly and were recovered by shooting or trapping less often than birds with necklace tags or with leg bands (P < 0.05 for juv and ad F). Survival was not affected by weight of necklaces (15 or 25 g) or by the color of the backpacks (white or brown). Necklace radio tags, at 2-3% of body weight, are more suitable than backpacks for studies of pheasant survival.
We conducted a pen study to determine the effects of radio tags on northern bobwhite (Colinus virginianus) body composition and survival. Two groups of 50 birds were fitted with radio tags using two attachment styles (backpack or bib); a third group of 50 birds with no radio tags served as controls. During 12 wk, we monitored weekly live body mass and lipid mass and noted whether tags were attached properly. After 12 wk, the birds were sacrificed and total body lipids, lean mass and water mass were determined. Body and lipid mass did not vary among groups before we attached tags. After 12 wk, tagged birds had significantly lower body weights and less lipid mass than controls. Birds with bibs had significantly lower survival rates than birds with backpacks. Most of the tagged birds (54%) experienced problems with their harnesses. Neither harness design was clearly superior because both designs had a high incidence of problems. Loss of lipids can reduce survival by reducing energy reserves and lower nesting success by reducing clutch size or delaying onset of ovulation. Harness problems may increase vulnerability of tagged birds to predation. Thus, estimates of survival and nesting effort obtained with radio-tagged quail may be biased. Alternative attachment designs should be evaluated, and alternatives to radio tags that are less stressful to the birds (e.g., whistle counts) should be favored when possible.
During 1987 and 1988, we tested the hypotheses that radio transmitter size (14 vs. 18-22 g) and signal strength (1-stage vs. 2-stage) had no effect on estimates of survival, movement, or home range of 54 female greater prairie-chickens (Tympanuchus cupido). Birds (n = 33) wearing heavier 2-stage solar transmitters, with twice the reflective surface, had lower (P = 0.08) estimated annual survival than birds (n = 21) wearing the lighter transmitter. In 2 of 3 seasons, estimates of daily movements, within-day movements, and seasonal ranges were larger (P < 0.09) for birds equipped with the more powerful 2-stage transmitters. Differences in estimated movements and home range did not represent true differences because long distance movements were more likely to be detected for birds wearing 2-stage units than for those equipped with 1-stage transmitters.
Scitation is the online home of leading journals and conference proceedings from AIP Publishing and AIP Member Societies
A leading text for undergraduate- and graduate-level courses, this book introduces widely used forms of remote sensing imagery and their applications in plant sciences, hydrology, earth sciences, and land use analysis. The text provides comprehensive coverage of principal topics and serves as a framework for organizing the vast amount of remote sensing information available on the Web. Featuring case studies and review questions, the book's 4 sections and 21 chapters are carefully designed as independent units that instructors can select from as needed for their courses. Illustrations include 29 color plates and over 400 black-and-white figures.
New to This Edition
Reflects significant technological and methodological advances.
Chapter on aerial photography now emphasizes digital rather than analog systems.
Updated discussions of accuracy assessment, multitemporal change detection, and digital preprocessing.
Links to recommended online videos and tutorials.
We compared the uses and definitions of habitat-related terms in 50 articles from 1980 to 1994 to operational definitions we derived from the literature. Only 9 (18%) of the arti- cles we reviewed defined and used habitat-related terms consistently and according to our definitions of the terms. Forty-seven articles used the term "habitat;" however, it was only defined and used consistent with our definition in 5 articles (11%) and was confused with vegetation association or defined incompletely in 42 papers (89%). "Habitat type" was the term most commonly used incorrectly; 16 of 17 times (94%) it was used to indi- cate vegetation association, but habitat and vegetation association are not synonymous. Authors did not provide definitions for habitat use, selection, preference, or availability 23 of 28 times (82%). We concluded that habitat terminology was used vaguely in 82% of the articles we reviewed. This distorts our communication with scientists in other dis- ciplines and alienates the public because we give ambiguous, indefinite, and unstandard- ized answers to ecological questions in public and legal situations. Scientists should de- fine and use habitat terminology operationally, so that the concepts are measurable and accurate. We must take the challenge to standardize terminology seriously, so that we can make meaningful statements to advance science.
Historical background, fundamental concepts, statistical considerations and a case study emphasize the need for absolute precision in applying remotely sensed data. This book is a complete guide to assessing the accuracy of maps generated from remotely sensed data.
Many rangelands in the southwestern United States provide quality habitat for Northern Bobwhites (Colinus virginianus). These same habitats are frequently managed for livestock production and thus are subjected to various brush management practices that are meant to enhance forage production. Bobwhites rely on woody cover for food, thermal and loafing cover, and protection from avian predators. Implementing brush management practices that reflect bobwhite requirements is important for managing usable space and viable populations. We described the structural vegetative characteristics associated with bobwhite locations and random locations on native rangelands in the upper Rolling Plains of Texas that are dominated by honey mesquite (Prosopis glandulosa) and managed with aerial herbicide and prescribed fire. We also used binary logistic regression to model habitat selection; the initial model was built using 67% of the data (n = 179 used-random paired points) and then validated using the remaining 33% of the data (n = 88 used-random paired points). Locations used by bobwhites had significantly larger mean values of percent brush canopy cover, visual obstruction, and angle of obstruction than did random locations; random locations had a greater mean value of percent bare ground than locations used by bobwhites. The resulting logistic regression model contained only the angle of obstruction; the model had an 80% probability of correctly classifying used and random locations based on the area under the receiver operating curve (ROC). The model maintained a high classification probability when applied to the smaller validation data set, with an area under the ROC of 0.78.
Having become suspicious of telemetry-based survival rates reported for northern bobwhites (Colinus virginianus), we surveyed the published record to determine whether reported survival rates were consistent with empirical expectations of production, for which there exists a vast database. If the production (juvenile/adult) required to stabilize a population at a reported or inferred annual survival rate was ≤7, we deemed the reported survival rate reasonable; otherwise, we deemed it not reasonable. We obtained 58 estimates of survival rates for unique points in space and time; 83% of these were not reasonable (apparently biased low). These results and supporting information strongly suggest (but do not necessarily prove) that radio packages (harness, transmitter, antenna) somehow handicap bobwhites. We recommend that researchers be extremely skeptical of telemetry data, plan telemetry studies such that independent data on population performance are available for comparison with telemetry estimates, and discuss the demographic implications of telemetry estimates. We also suggest that radiotelemetry might not always be appropriate for a given research question and that alternative methods be employed whenever possible.
Radiotelemetry has been widely used in northern bobwhite (Colinus virginianus) research to estimate survival rates and other demographic parameters. Biologists have used this knowledge to study bobwhite ecology, develop management theory, and base management actions. We tested the assumption that radiotransmitters do not bias survival rates of bobwhites by comparing survival rates of banded bobwhites with and without radiotransmitters on Tall Timbers Research Station (TTRS) from 1999 to 2004. We used Burnham's model in Program MARK and model-selection procedures to determine relative importance of year, gender, and radiotagged status on annual survival rates and recovery processes. Three plausible models (relative quasi-likelihood Akaike's Information Criterion [ΔQAICc] < 3) included year dependence in survival and an additive effect of gender but no radiotransmitter effect. Models including a radiotransmitter effect in survival were >8 ΔQAICc from the top models, had low Akaike model weights (wi < 0.007), and low importance weight (S̀wi(radio) = 0.01). We also compared band—recapture survival estimates from the QAICc minimizing model to staggered entry Kaplan—Meier (KM) survival estimates from 2000 to 2003. Annual KM survival estimates of male and female bobwhites were within the 95% confidence interval of band—recapture estimates in 7 of 8 comparisons. We conclude that radiotelemetry is a reliable technique for determining bobwhite survival. Managers should view information from properly conducted telemetry research as reliable and useful for management.
Radiotelemetry has become an important and frequently used tool in wildlife research. Inferences drawn from radiotelemetry data depend on the assumption that the radiotransmitters are not influencing parameter(s) of interest. An article by Guthery and Lusk (2004) in the Wildlife Society Bulletin questioned the validity of this assumption for estimating survival rates of northern bobwhites (Colinus virginianus) using radiotelemetry data. In this evaluation, we address technical and philosophical flaws in Guthery and Lusk's (2004) critique of northern bobwhite studies utilizing radiotelemetry. They concluded that biologists should be skeptical of radiotelemetry studies and they advised researchers to design studies to address potential biases caused by radiotransmitters using independent data. Although we agree that researchers are responsible for testing key assumptions of their techniques, we believe Guthery and Lusk's (2004) conclusions were not well supported and were based on tenuous assumptions. Guthery and Lusk (2004) calculated the level of productivity (given as a fall age ratio) required to balance a simple population model that contained published estimates of annual survival and assumed an annual finite population growth rate of 1.0. We review their population model and show that the relationship between an annual survival rate and fall age ratio is nonlinear. This nonlinearity can lead to biased estimates of a fall age ratio, especially at lower values of annual survival. We also question the validity of using fall age ratios as an estimator of productivity. Further, we suggest that this assessment of a radiotransmitter effect from a survival rate itself is not appropriate. This rate can be depressed (or elevated) for a variety of reasons not related to the influence of radiotransmitters. In addition, Guthery and Lusk (2004) assumed that daily survival rates (as calculated from both annual and seasonal published estimates) were constant throughout the year; thus, they scaled daily survival rates from seasonal to annual estimates. Further, their meta-analysis was hindered by temporal pseudoreplication and a lack of independence among the observations used in the analysis. We conclude the weight of the evidence presented by Guthery and Lusk (2004) is not as strong as they claim because it fails to meet the test of sufficient causation. While scientists should always be skeptical and critical of assumptions of all methods employed in wildlife research, more rigorous tests are necessary before we discredit a valuable technique without sufficient empirical evidence.
Numerous studies of behavior and ecology of northern bobwhites (Colinus virginianus) have depended on radiotagging and telemetry for data collection. Excluding the presumably short-term effects of trapping, handling, and attaching radiotransmitters, researchers often assume that little bias is associated with estimating survival and behavioral parameters associated with this technique. However, researchers have not adequately examined these effects on organisms being investigated and have thus assumed demographic information obtained from such methods are valid. In light of this conjecture, it is imperative to evaluate methodological assumptions to ensure research is statistically valid and biologically meaningful. Therefore, we used Burnham's model and program MARK to analyze survival estimates of individually banded and radiotagged bobwhites during an 8-year period (1997–2004) consisting of 6,568 individuals (2,527 radiotagged) via combined analysis of mark—recapture, dead recovery (via harvest), and radiotelemetry data to test the effects of radiotransmitters on bobwhite survival. We also compared band—recapture survival estimates to Kaplan—Meier survival estimates, and we examined the effects of various other factors (e.g., temporal, spatial) on bobwhite survival. Based on Akaike's model selection criterion, the best model including the radiotransmitter covariate (Akaike's Information Criterion adjusted for small sample size bias and overdispersion relative value = 0.72) did not explain more of the variation in survival than models without this effect. Thus, we found the effect of radiotransmitters as negligible. Bobwhite survival varied relative to spatial (e.g., site), temporal (e.g., yr and season), and gender effects. Average annual survival for the 8-year period was 22.76% (1.50 SE) for banded-only and 21.72% (1.49 SE) for radiotagged birds. Survival rate varied annually, ranging from 12.42% (7.51 SE) to 37.16% (8.27 SE), and seasonally, ranging from 23.82% (2.71 SE) to 65.06% (3.23 SE); however, between group (banded-only, radiotagged) survival differences were still inconsequential. We conclude that for our study, radiotelemetry provided reliable survival estimates of an intensively managed bobwhite population, where supplemental food was provided, and this information provided useful data to make practical habitat management decisions. We believe that future radiotelemetry studies would benefit as a whole if researchers conducted similar analyses prior to presenting their results from radiotelemetry data, especially for populations that are more food limited.
Radio-telemetry is often the method of choice for Studies of species whose behaviour is difficult to observe directly. However, considerable debate has ensued about the best way of deriving home-range estimates. In recent years, kernel estimators have become the most widely used method, together with the oldest and simplest method, the minimum convex polygon (MCP). More recently, it has been Suggested that the local convex hull (LCH) might be more appropriate than kernel methods in cases where an animal's home range includes a priori inaccessible areas. Yet another method, the Brownian bridge (BB), explicitly uses autocorrelated data to determine movement paths and, ultimately, home ranges or migration routes of animals. Whereas several studies have used Simulation techniques to compare these different methods, few have used data from real animals. We used radio-telemetric data from urban badgers Meles meles to compare two sampling protocols (10-minute vs at least 30-minute inter-fix intervals) and four home-range estimators (MCP, fixed kernels (FK), LCH and BB). We used a multi-response permutation procedure and randomisation tests to compare overall patterns of fixes and degree of overlap of home ranges estimated using data from different sampling protocols, and a general linear model to compare the influence of sampling protocols and home-range estimator on the size of habitat patches. The shape of the estimated home ranges was influenced by sampling protocol in some cases. By contrast, the sizes and proportions of different habitats within home ranges were influenced by estimator type but not by sampling protocol. LCH performed consistently better than FK, and is especially appropriate for patchy study areas containing frequent no-go zones. However, we recommend using LCH in combination with other methods to estimate total range size, because LCH tended to produce smaller estimates than any other method. Results relating to BB are preliminary but suggest that this method is unsuitable for species in which range size is small compared to average travel speed.
New demands on our land resources require more stringent controls and management practices. The administration of these controls requires better and more frequent information concerning land use. Although new tools became available to aid in acquiring and processing the data, a major lack in uniform techniques for identifying the land use was a major problem. Creation of a more standard form of classification of land use, based on the capabilities inherent in the various forms of remote sensors and other data sources was a necessary step.A classification has been created, and published in preliminary form, by the Geological Survey of the United States Department of Interior. It is presented as Geological Survey 671, entitled "A Land Use Classification System for Use With Remote Sensor Data". This paper discusses the origin, development, and controlling influences of that classification system.
By studying animal movements, researchers can gain insight into many of the ecological characteristics and processes important for understanding population-level dynamics. We developed a Brownian bridge movement model (BBMM) for estimating the expected movement path of an animal, using discrete location data obtained at relatively short time intervals. The BBMM is based on the properties of a conditional random walk between successive pairs of locations, dependent on the time between locations, the distance between locations, and the Brownian motion variance that is related to the animal's mobility. We describe two critical developments that enable widespread use of the BBMM, including a derivation of the model when location data are measured with error and a maximum likelihood approach for estimating the Brownian motion variance. After the BBMM is fitted to location data, an estimate of the animal's probability of occurrence can be generated for an area during the time of observation. To illustrate potential applications, we provide three examples: estimating animal home ranges, estimating animal migration routes, and evaluating the influence of fine-scale resource selection on animal movement patterns.
Radiolocation telemetry. Pages 95-103
- R B Brander
- W W Cochran
Brander, R. B., and W. W. Cochran. 1969. Radiolocation telemetry. Pages 95-103, in
R. H. Giles, editor. Wildlife Management Techniques Manual. The Wildlife
Society, Washington, D. C., USA.