scholarly journals Estimating Detection Probablities of River Birds using Double Surveys

The Auk ◽  
2006 ◽  
Vol 123 (3) ◽  
pp. 695-707 ◽  
Author(s):  
Robert J. Fletcher ◽  
Richard L. Hutto
Keyword(s):  
Spatial Scales ◽  
Rapid Assessment ◽  
Mass Detection ◽  
Information Theoretic ◽  
Modeling Process ◽  
Detection Probabilities ◽  
Survey Technique ◽  
River Reach ◽  
Viable Method ◽  
Combined Detection

AbstractWe describe a method for surveying birds in river habitats that allows for rapid assessment across broad spatial scales and estimation of detection probabilities. Our river survey approach incorporates a double-survey technique, whereby observers in two canoes simultaneously survey birds along a river reach. Data are in the form of a two-sample mark-recapture history, and covariates suspected of influencing detection probabilities can be included in the modeling process and evaluated using information-theoretic approaches. We provide an example using the method along the Madison and upper Missouri rivers in Montana. Overall, detection probabilities for each observer ranged from 57% to 89%, and combined detection probabilities (the likelihood of at least one observer detecting an individual) were consistently high (88% across all species). Detection probabilities across species were positively correlated with body mass. Detection probabilities for some species were influenced by observer, river conditions, and whether species were in groups or alone; groups were more detectable, and individuals in slow-flowing and wide sections of river were more detectable. Boat-based double surveys are a viable method for estimating detection probabilities of birds in river habitats, and double surveys should be considered in other aquaticEstimaciones de Probabilidades de Detección de Aves de Río Utilizando Muestreos Dobles systems.

scholarly journals Overcoming the challenges of measuring the abundance of a cryptic macropod: is a qualitative approach good enough?

2014 ◽  
Vol 41 (1) ◽  
pp. 84 ◽  
Author(s):  
Karlene Bain ◽  
Adrian Wayne ◽  
Roberta Bencini
Keyword(s):  
Population Size ◽  
Relative Abundance ◽  
Spatial Scales ◽  
Faecal Pellet ◽  
Survey Method ◽  
Population Abundance ◽  
Mark Recapture ◽  
Survey Technique ◽  
Threatened Taxa ◽  
Activity Indices

Context An understanding of population size and status is necessary for the implementation of appropriate conservation measures to recover threatened taxa. Mark–recapture studies at large spatial scales are impractical and expensive and a rapid survey technique is an attractive option to provide a measure of relative abundance for cryptic species, using indicators of activity. Aims The aim of our study was to use conventional methods for population estimation to calibrate a rapid survey technique for the quokka (Setonix brachyurus) in the southern forests of Western Australia, with a view to providing quantitative outcomes from this widely adopted monitoring approach. Methods We evaluated the accuracy of relative abundances obtained from the rapid survey technique by comparing them with abundance estimates obtained through established methods for the estimation of populations, including web-based mark–recapture and transect-based counts of activity indicators and sightings. Key results The rapid survey technique was effective at determining presence of quokkas but resulted in an over-estimation of population size because of inaccurate assumptions about occupancy and relative abundance of animals. An alternative survey method based on counts of fresh faecal-pellet groups was found to provide a more reliable and practical estimation of population abundance (R2 = 0.97). Conclusions Activity indices can be used to quantify population abundance, but only for indicators of activity that can be detected readily and for which freshness of activity can be determined. Implications Our findings suggest that a rapid survey based on activity indices can be used to evaluate quantitatively the population size of a species that is rare and potentially mobile at a landscape scale. The attraction of these techniques is that they provide a rapid and inexpensive survey option that is potentially applicable to any cryptic and/or threatened species and is practical for resource-constrained land managers.

Habitat selection by nesting and brood-rearing sharp-tailed grouse

2009 ◽  
Vol 87 (4) ◽  
pp. 326-336 ◽  
Author(s):  
Alicia D. Goddard ◽  
Russell D. Dawson ◽  
Michael P. Gillingham
Keyword(s):  
Spatial Scales ◽  
Conditional Logistic Regression ◽  
Habitat Type ◽  
Theoretic Approach ◽  
Information Theoretic ◽  
Logistic Regression Models ◽  
Brood Rearing ◽  
Shrub Steppe ◽  
Information Theoretic Approach ◽  
Selection Of

Breeding success is a critical component of population stability and is often influenced by the habitats used during the breeding season. Current hypotheses suggest that sharp-tailed grouse ( Tympanuchus phasianellus (L., 1758)) select nest and brood-rearing habitats that provide both lateral and overhead cover to avoid detection by predators. We examined the selection of nesting and brood-rearing habitats of sharp-tailed grouse at three spatial scales (landscape, patch, and site) in northeastern British Columbia using standard and conditional logistic regression models and an information–theoretic approach. At the patch and site scales, our results validate our predictions, as nesting females selected shrub–steppe habitats, greater shrub and grass cover, taller vegetation, and greater residual vegetation compared with random sites. Brood-rearing females selected for agricultural habitats during the early brood-rearing period (0–14 days), but did not show selection of any habitat type or site attribute during the late brood-rearing period (15–49 days). We suggest that the selection of shrub-dominated habitats by nesting females supports the hypothesis that females select sites and habitats that maximize concealment. We further suggest that selection of shrub-dominated habitat is occurring in response to changes in habitat conditions and availability, as natural grassland communities have diminished across the landscape.

scholarly journals An example of SAR-derived image segmentation for landslides detection

2018 ◽  
Author(s):  
Giuseppe Esposito ◽  
Alessandro Cesare Mondini ◽  
Ivan Marchesini ◽  
Paola Reichenbach ◽  
Paola Salvati ◽  
...  
Keyword(s):  
Spatial Scales ◽  
Rapid Assessment ◽  
Ground Truth ◽  
Radar Data ◽  
Mass Movements ◽  
Ground Truth Data ◽  
Before And After ◽  
Satellite Radar ◽  
Gis Software ◽  
Derived Data

A rapid assessment of the areal extent of landslide disasters is one of the main challenges facing by the scientific community. Satellite radar data represent a powerful tool for the rapid detection of landslides over large spatial scales, even in case of persistent cloud cover. To define landslide locations, radar data need to be firstly pre-processed and then elaborated for the extraction of the required information. Segmentation represents one of the most useful procedures for identifying land cover changes induced by landslides. In this study, we present an application of the i.segment module of GRASS GIS software for segmenting radar-derived data. As study area, we selected the Tagari River valley in Papua New Guinea, where massive landslides were triggered by a M7.5 earthquake on February 25, 2018. A comparison with ground truth data revealed a suitable performance of i.segment. Particular segmentation patterns, in fact, resulted in the areas affected by landslides with respect to the external ones, or to the same areas before the earthquake. These patterns highlighted a relevant contrast of radar backscattering values recorded before and after the landslides. With our procedure, we were able to define the extension of the mass movements that occurred in the study area, just three days after the M7.5 earthquake.

scholarly journals An example of SAR-derived image segmentation for landslides detection

2018 ◽  
Author(s):  
Giuseppe Esposito ◽  
Alessandro Cesare Mondini ◽  
Ivan Marchesini ◽  
Paola Reichenbach ◽  
Paola Salvati ◽  
...  
Keyword(s):  
Spatial Scales ◽  
Rapid Assessment ◽  
Ground Truth ◽  
Radar Data ◽  
Mass Movements ◽  
Ground Truth Data ◽  
Before And After ◽  
Satellite Radar ◽  
Gis Software ◽  
Derived Data

A rapid assessment of the areal extent of landslide disasters is one of the main challenges facing by the scientific community. Satellite radar data represent a powerful tool for the rapid detection of landslides over large spatial scales, even in case of persistent cloud cover. To define landslide locations, radar data need to be firstly pre-processed and then elaborated for the extraction of the required information. Segmentation represents one of the most useful procedures for identifying land cover changes induced by landslides. In this study, we present an application of the i.segment module of GRASS GIS software for segmenting radar-derived data. As study area, we selected the Tagari River valley in Papua New Guinea, where massive landslides were triggered by a M7.5 earthquake on February 25, 2018. A comparison with ground truth data revealed a suitable performance of i.segment. Particular segmentation patterns, in fact, resulted in the areas affected by landslides with respect to the external ones, or to the same areas before the earthquake. These patterns highlighted a relevant contrast of radar backscattering values recorded before and after the landslides. With our procedure, we were able to define the extension of the mass movements that occurred in the study area, just three days after the M7.5 earthquake.

Occupancy Modeling of Woodpeckers: Maximizing Detections for Multiple Species With Multiple Spatial Scales

2014 ◽  
Vol 5 (2) ◽  
pp. 198-207 ◽  
Author(s):  
Jeremy A. Baumgardt ◽  
Joel D. Sauder ◽  
Kerry L. Nicholson
Keyword(s):  
Detection Probability ◽  
Spatial Scales ◽  
Parameter Estimates ◽  
Management Decisions ◽  
Point Counts ◽  
Area Of Occupancy ◽  
Unit Scale ◽  
Detection Probabilities ◽  
Pileated Woodpeckers ◽  
Multiple Species

Abstract Numerous forest birds benefit from woodpecker presence or have similar habitat requirements. Monitoring populations of forest woodpeckers can be useful for management decisions regarding these and other forest species. Usefulness of monitoring efforts depends on methods used and the quality of resulting parameter estimates. Estimating the proportion of area occupied by a species can be an attractive and affordable alternative to abundance or survival estimates. The purpose of this study was to assess the distribution and area of occupancy for pileated woodpeckers (Drycopus pileatus) and American three-toed woodpeckers (Picoides dorsalis) in north-central Idaho, and to compare occupancy estimates using silent point counts, playback surveys, and playback surveys that incorporated estimates of detection probability (p). We used a hierarchical multiscale framework that allowed estimation of occupancy at two spatial scales and applied a removal design such that repeat visits to sampling stations was not necessary to estimate p. The initial naïve estimate of occupancy (using presence–absence data) for pileated woodpecker was 0.39, which increased to 0.59 using playback surveys. The corrected estimate of occupancy at the 1-km2 unit scale was 0.70. The naïve estimates of occupancy for American three-toed woodpeckers using silent point counts and playback surveys were 0.14 and 0.34, respectively. The unbiased estimate of occupancy at the 1-km2 unit scale was 0.71. Detection probabilities are known to vary spatially and temporally for numerous reasons. Thus, comparisons of naïve estimates of occupancy to monitor forest woodpeckers would be imprudent and could lead to poor management decisions. We recommend incorporating detection probability for monitoring wildlife species and show how this can be done within a single sampling framework for species that utilize the landscape at disparate scales.

scholarly journals Large-scale distribution patterns of carnivores in northern South Africa: implications for conservation and monitoring

Oryx ◽  
2011 ◽  
Vol 45 (4) ◽  
pp. 579-586 ◽  
Author(s):  
Michelle Thorn ◽  
Matthew Green ◽  
Mark Keith ◽  
Kelly Marnewick ◽  
Philip W. Bateman ◽  
...  
Keyword(s):  
South Africa ◽  
Large Scale ◽  
Extinction Risk ◽  
Spatial Scales ◽  
Rapid Assessment ◽  
Distribution Patterns ◽  
Distribution Data ◽  
Acinonyx Jubatus ◽  
Baseline Information ◽  
Local Range

AbstractAccurate assessment of carnivore population status is frequently hindered by insufficient distribution data. For northern South Africa we address this deficit by mapping new records from landscape-scale sign surveys, questionnaire interviews, problem animal records and camera trapping. The black-backed jackal Canis mesomelas and caracal Caracal caracal remain common and widespread. Ranges of the serval Leptailurus serval and brown hyaena Hyaena brunnea were much larger than previous estimates, reducing the risk of simultaneous extirpation across all occupied locations. The proportion of range area occupied was larger for several species, notably the leopard Panthera pardus, cheetah Acinonyx jubatus and serval. We conclude that the serval continues to recover from historical threats and is expanding into new areas. A larger brown hyaena range and less fragmented pattern of occurrence probably confers greater resilience to threats than was suggested by previous data. Reduced extinction risk arising from the increased area occupied by the cheetah and leopard is tempered by probable local range contraction. Our maps provide baseline information for monitoring the distribution of these six species, which is essential in managing ecological issues that have a spatial component such as responses to changing land use. Our results also demonstrate the utility of detection/non-detection surveys in rapid assessment of carnivore populations at large spatial scales.

scholarly journals Rapid assessment of fruit-color selection by birds using artificial fruits at local scale in Central Amazonia

2008 ◽  
Vol 38 (2) ◽  
pp. 291-296 ◽  
Author(s):  
Rafael Arruda ◽  
Domingos J. Rodrigues ◽  
Thiago J. Izzo
Keyword(s):  
Spatial Scales ◽  
Rapid Assessment ◽  
Bird Community ◽  
Fruit Color ◽  
Frugivorous Birds ◽  
Low Contrast ◽  
Color Selection ◽  
Ecological Experiments ◽  
Central Amazonia ◽  
Selective Forces

Modeling clays have been used in several ecological experiments and have proved to be an important tool to variables control. The objective of our study was to determine if fruit color in isolated and grouped displays influences the fruit selection by birds in the field using artificial fruits. Data were collected in six plots distributed homogeneously in 3 km long trails with a minimum distance of 0.5 km. We used a paired experimental design to establish our experiments, so that all treatments were available to the local bird community in each plot. Overall, red was more pecked than brown and white. Isolated red and brown displays were significantly more pecked than others display. Even though our study was conducted in small spatial scales, artificial fruits appeared to be efficient in register fruit consumption attempts by bird. Although inconclusive about selective forces that sharp the dynamics of fruit color polymorphisms and choice by frugivorous birds, our findings corroborate recent studies wherein birds showed preferences by high- over low-contrast fruit signals.

scholarly journals An example of SAR-derived image segmentation for landslides detection

2018 ◽  
Author(s):  
Giuseppe Esposito ◽  
Alessandro Cesare Mondini ◽  
Ivan Marchesini ◽  
Paola Reichenbach ◽  
Paola Salvati ◽  
...  
Keyword(s):  
Spatial Scales ◽  
Rapid Assessment ◽  
Ground Truth ◽  
Radar Data ◽  
Mass Movements ◽  
Ground Truth Data ◽  
Before And After ◽  
Satellite Radar ◽  
Gis Software ◽  
Derived Data

A rapid assessment of the areal extent of landslide disasters is one of the main challenges facing by the scientific community. Satellite radar data represent a powerful tool for the rapid detection of landslides over large spatial scales, even in case of persistent cloud cover. To define landslide locations, radar data need to be firstly pre-processed and then elaborated for the extraction of the required information. Segmentation represents one of the most useful procedures for identifying land cover changes induced by landslides. In this study, we present an application of the i.segment module of GRASS GIS software for segmenting radar-derived data. As study area, we selected the Tagari River valley in Papua New Guinea, where massive landslides were triggered by a M7.5 earthquake on February 25, 2018. A comparison with ground truth data revealed a suitable performance of i.segment. Particular segmentation patterns, in fact, resulted in the areas affected by landslides with respect to the external ones, or to the same areas before the earthquake. These patterns highlighted a relevant contrast of radar backscattering values recorded before and after the landslides. With our procedure, we were able to define the extension of the mass movements that occurred in the study area, just three days after the M7.5 earthquake.

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