The Experts below are selected from a list of 141 Experts worldwide ranked by ideXlab platform
Pedro Beja - One of the best experts on this subject based on the ideXlab platform.
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the role of conservative versus innovative nesting behavior on the 25 year population expansion of an avian predator
Ecology and Evolution, 2017Co-Authors: Andreia Dias, Luis Palma, Filipe Carvalho, Dora R Neto, Joan Real, Pedro BejaAbstract:Species ranges often change in relation to multiple environmental and demographic factors. Innovative behaviors may affect these changes by facilitating the use of novel habitats, although this idea has been little explored. Here, we investigate the importance of behavior during range change, using a 25-year population expansion of Bonelli's eagle in southern Portugal. This unique population is almost exclusively tree nesting, while all other populations in western Europe are predominantly cliff nesting. During 1991-2014, we surveyed nest sites and estimated the year when each breeding territory was established. We approximated the boundaries of 84 territories using Dirichlet Tessellation and mapped topography, land cover, and the density of human infrastructures in buffers (250, 500, and 1,000 m) around nest and random sites. We then compared environmental conditions at matching nest and random sites within territories using conditional logistic regression, and used quantile regression to estimate trends in nesting habitats in relation to the year of territory establishment. Most nests (>85%, n = 197) were in eucalypts, maritime pines, and cork oaks. Nest sites were farther from the nests of neighboring territories than random points, and they were in areas with higher terrain roughness, lower cover by agricultural and built-up areas, and lower road and powerline densities. Nesting habitat selection varied little with year of territory establishment, although nesting in eucalypts increased, while cliff nesting and cork oak nesting, and terrain roughness declined. Our results suggest that the observed expansion of Bonelli's eagles was facilitated by the tree nesting behavior, which allowed the colonization of areas without cliffs. However, all but a very few breeding pairs settled in habitats comparable to those of the initial population nucleus, suggesting that after an initial trigger possibly facilitated by tree nesting, the habitat selection remained largely conservative. Overall, our study supports recent calls to incorporate information on behavior for understanding and predicting species range shifts.
Andreia Dias - One of the best experts on this subject based on the ideXlab platform.
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the role of conservative versus innovative nesting behavior on the 25 year population expansion of an avian predator
Ecology and Evolution, 2017Co-Authors: Andreia Dias, Luis Palma, Filipe Carvalho, Dora R Neto, Joan Real, Pedro BejaAbstract:Species ranges often change in relation to multiple environmental and demographic factors. Innovative behaviors may affect these changes by facilitating the use of novel habitats, although this idea has been little explored. Here, we investigate the importance of behavior during range change, using a 25-year population expansion of Bonelli's eagle in southern Portugal. This unique population is almost exclusively tree nesting, while all other populations in western Europe are predominantly cliff nesting. During 1991-2014, we surveyed nest sites and estimated the year when each breeding territory was established. We approximated the boundaries of 84 territories using Dirichlet Tessellation and mapped topography, land cover, and the density of human infrastructures in buffers (250, 500, and 1,000 m) around nest and random sites. We then compared environmental conditions at matching nest and random sites within territories using conditional logistic regression, and used quantile regression to estimate trends in nesting habitats in relation to the year of territory establishment. Most nests (>85%, n = 197) were in eucalypts, maritime pines, and cork oaks. Nest sites were farther from the nests of neighboring territories than random points, and they were in areas with higher terrain roughness, lower cover by agricultural and built-up areas, and lower road and powerline densities. Nesting habitat selection varied little with year of territory establishment, although nesting in eucalypts increased, while cliff nesting and cork oak nesting, and terrain roughness declined. Our results suggest that the observed expansion of Bonelli's eagles was facilitated by the tree nesting behavior, which allowed the colonization of areas without cliffs. However, all but a very few breeding pairs settled in habitats comparable to those of the initial population nucleus, suggesting that after an initial trigger possibly facilitated by tree nesting, the habitat selection remained largely conservative. Overall, our study supports recent calls to incorporate information on behavior for understanding and predicting species range shifts.
Filipe Carvalho - One of the best experts on this subject based on the ideXlab platform.
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the role of conservative versus innovative nesting behavior on the 25 year population expansion of an avian predator
Ecology and Evolution, 2017Co-Authors: Andreia Dias, Luis Palma, Filipe Carvalho, Dora R Neto, Joan Real, Pedro BejaAbstract:Species ranges often change in relation to multiple environmental and demographic factors. Innovative behaviors may affect these changes by facilitating the use of novel habitats, although this idea has been little explored. Here, we investigate the importance of behavior during range change, using a 25-year population expansion of Bonelli's eagle in southern Portugal. This unique population is almost exclusively tree nesting, while all other populations in western Europe are predominantly cliff nesting. During 1991-2014, we surveyed nest sites and estimated the year when each breeding territory was established. We approximated the boundaries of 84 territories using Dirichlet Tessellation and mapped topography, land cover, and the density of human infrastructures in buffers (250, 500, and 1,000 m) around nest and random sites. We then compared environmental conditions at matching nest and random sites within territories using conditional logistic regression, and used quantile regression to estimate trends in nesting habitats in relation to the year of territory establishment. Most nests (>85%, n = 197) were in eucalypts, maritime pines, and cork oaks. Nest sites were farther from the nests of neighboring territories than random points, and they were in areas with higher terrain roughness, lower cover by agricultural and built-up areas, and lower road and powerline densities. Nesting habitat selection varied little with year of territory establishment, although nesting in eucalypts increased, while cliff nesting and cork oak nesting, and terrain roughness declined. Our results suggest that the observed expansion of Bonelli's eagles was facilitated by the tree nesting behavior, which allowed the colonization of areas without cliffs. However, all but a very few breeding pairs settled in habitats comparable to those of the initial population nucleus, suggesting that after an initial trigger possibly facilitated by tree nesting, the habitat selection remained largely conservative. Overall, our study supports recent calls to incorporate information on behavior for understanding and predicting species range shifts.
Henk W Venema - One of the best experts on this subject based on the ideXlab platform.
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determination of nearest neighbours in muscle fibre patterns using a generalized version of the Dirichlet Tessellation
Pattern Recognition Letters, 1991Co-Authors: Henk W VenemaAbstract:Nearest neighbours in muscle fibre patterns can be determined using a generalized version of the Dirichlet Tessellation, based on the construction of radical axes of circles. Remaining errors are removed by an iterative post-processing algorithm.
J.f. Peters - One of the best experts on this subject based on the ideXlab platform.
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voronoi region based adaptive unsupervised color image segmentation
Pattern Recognition, 2017Co-Authors: R Hettiarachchi, J.f. PetersAbstract:Color image segmentation is a crucial step in many computer vision and pattern recognition applications. This paper introduces an adaptive and unsupervised approach based on Voronoi regions to solve the color image segmentation problem. The proposed method uses a hybrid of spatial and feature space Dirichlet Tessellation followed by inter-Voronoi region proximal cluster merging to automatically find the number of clusters and cluster centroids in an image. Since, the Voronoi regions are much smaller compared to the whole image, Voronoi region-wise clustering improves the efficiency and accuracy of the number of clusters and cluster centroid estimation process. The proposed method was compared with four other adaptive unsupervised cluster-based image segmentation algorithms on three image segmentation evaluation benchmarks. The experimental results reported in this paper confirm that the proposed method outperforms the existing algorithms in terms of the image segmentation quality and results in much lower average execution time per image. HighlightsWe propose a hybrid of Dirichlet Tessellation to automatically segment an image.Spatial Dirichlet Tessellation adaptively divides an image into Voronoi regions.Feature space Dirichlet Tessellation adaptively clusters pixels in Voronoi regions.Inter-Voronoi region proximal cluster merging automatically finds the final clusters.