William Link, Ph.D. (Former Employee)
Science and Products
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Tigers and their prey: Predicting carnivore densities from prey abundance
The goal of ecology is to understand interactions that determine the distribution and abundance of organisms. In principle, ecologists should be able to identify a small number of limiting resources for a species of interest, estimate densities of these resources at different locations across the landscape, and then use these estimates to predict the density of the focal species at these locations
Authors
K. U. Karanth, J. D. Nichols, S. Kumar, W. A. Link, J. E. Hines
Hierarchial mark-recapture models: a framework for inference about demographic processes
The development of sophisticated mark-recapture models over the last four decades has provided fundamental tools for the study of wildlife populations, allowing reliable inference about population sizes and demographic rates based on clearly formulated models for the sampling processes. Mark-recapture models are now routinely described by large numbers of parameters. These large models provide the
Authors
W. A. Link, R. J. Barker
Whole-ecosystem experiments: replication and arguing from error: commentary
No abstract available.
Authors
W. A. Link
Estimation of change in populations and communities from monitoring survey data
Monitoring surveys provide fundamental information for use in environmental decision making by permitting assessment of both current population (or community) status and change in status, by providing a historical context of the present status, and by documenting response to ongoing management. Conservation of species and communities has historically been based upon monitoring information, and pr
Authors
J.R. Sauer, W. A. Link, J. D. Nichols
Hierarchical models and the analysis of bird survey information
Management of birds often requires analysis of collections of estimates. We describe a hierarchical modeling approach to the analysis of these data, in which parameters associated with the individual species estimates are treated as random variables, and probability statements are made about the species parameters conditioned on the data. A Markov-Chain Monte Carlo (MCMC) procedure is used to fi
Authors
J.R. Sauer, W. A. Link
Demographic analysis from summaries of an age-structured population
Demographic analyses of age-structured populations typically rely on life history data for individuals, or when individual animals are not identified, on information about the numbers of individuals in each age class through time. While it is usually difficult to determine the age class of a randomly encountered individual, it is often the case that the individual can be readily and reliably assig
Authors
William A. Link, J. Andrew Royle, Jeff S. Hatfield
Nonidentifiability of population size from capture-recapture data with heterogeneous detection probabilities
Heterogeneity in detection probabilities has long been recognized as problematic in mark-recapture studies, and numerous models developed to accommodate its effects. Individual heterogeneity is especially problematic, in that reasonable alternative models may predict essentially identical observations from populations of substantially different sizes. Thus even with very large samples, the analyst
Authors
W. A. Link
Individual covariation in life-history traits: Seeing the trees despite the forest
We investigated the influence of age on survival and breeding rates in a long-lived species Rissa tridactyla using models with individual random effects permitting variation and covariation in fitness components among individuals. Differences in survival or breeding probabilities among individuals are substantial, and there was positive covariation between survival and breeding probability; birds
Authors
E. Cam, W. A. Link, E.G. Cooch, J. -Y. Monnat, E. Danchin
Model-based estimation of individual fitness
Fitness is the currency of natural selection, a measure of the propagation rate of genotypes into future generations. Its various definitions have the common feature that they are functions of survival and fertility rates. At the individual level, the operative level for natural selection, these rates must be understood as latent features, genetically determined propensities existing at birth. Thi
Authors
William A. Link, Evan G. Cooch, Emmanuelle Cam
Using Christmas Bird Count data in analysis of population change
The scientific credibility of Christmas Bird Count (CBC) results depend on the development and implementation of appropriate methods of statistical analysis. The key to any successful analysis of CBC data is to begin with a careful review of how the limitations of the data are likely to influence the results of the analysis, then to choose methods of analysis that accommodate as much as possible
Authors
J.R. Sauer, W. A. Link
Hierarchical modeling of population stability and species group attributes from survey data
Many ecological studies require analysis of collections of estimates. For example, population change is routinely estimated for many species from surveys such as the North American Breeding Bird Survey (BBS), and the species are grouped and used in comparative analyses. We developed a hierarchical model for estimation of group attributes from a collection of estimates of population trend. The
Authors
J.R. Sauer, W. A. Link
Random effects and shrinkage estimation in capture-recapture models
We discuss the analysis of random effects in capture-recapture models, and outline Bayesian and frequentists approaches to their analysis. Under a normal model, random effects estimators derived from Bayesian or frequentist considerations have a common form as shrinkage estimators. We discuss some of the difficulties of analysing random effects using traditional methods, and argue that a Bayesia
Authors
J. Andrew Royle, W. A. Link
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Filter Total Items: 44No results found.
- Publications
Filter Total Items: 124
Tigers and their prey: Predicting carnivore densities from prey abundance
The goal of ecology is to understand interactions that determine the distribution and abundance of organisms. In principle, ecologists should be able to identify a small number of limiting resources for a species of interest, estimate densities of these resources at different locations across the landscape, and then use these estimates to predict the density of the focal species at these locationsAuthorsK. U. Karanth, J. D. Nichols, S. Kumar, W. A. Link, J. E. HinesHierarchial mark-recapture models: a framework for inference about demographic processes
The development of sophisticated mark-recapture models over the last four decades has provided fundamental tools for the study of wildlife populations, allowing reliable inference about population sizes and demographic rates based on clearly formulated models for the sampling processes. Mark-recapture models are now routinely described by large numbers of parameters. These large models provide theAuthorsW. A. Link, R. J. BarkerWhole-ecosystem experiments: replication and arguing from error: commentary
No abstract available.AuthorsW. A. LinkEstimation of change in populations and communities from monitoring survey data
Monitoring surveys provide fundamental information for use in environmental decision making by permitting assessment of both current population (or community) status and change in status, by providing a historical context of the present status, and by documenting response to ongoing management. Conservation of species and communities has historically been based upon monitoring information, and prAuthorsJ.R. Sauer, W. A. Link, J. D. NicholsHierarchical models and the analysis of bird survey information
Management of birds often requires analysis of collections of estimates. We describe a hierarchical modeling approach to the analysis of these data, in which parameters associated with the individual species estimates are treated as random variables, and probability statements are made about the species parameters conditioned on the data. A Markov-Chain Monte Carlo (MCMC) procedure is used to fiAuthorsJ.R. Sauer, W. A. LinkDemographic analysis from summaries of an age-structured population
Demographic analyses of age-structured populations typically rely on life history data for individuals, or when individual animals are not identified, on information about the numbers of individuals in each age class through time. While it is usually difficult to determine the age class of a randomly encountered individual, it is often the case that the individual can be readily and reliably assigAuthorsWilliam A. Link, J. Andrew Royle, Jeff S. HatfieldNonidentifiability of population size from capture-recapture data with heterogeneous detection probabilities
Heterogeneity in detection probabilities has long been recognized as problematic in mark-recapture studies, and numerous models developed to accommodate its effects. Individual heterogeneity is especially problematic, in that reasonable alternative models may predict essentially identical observations from populations of substantially different sizes. Thus even with very large samples, the analystAuthorsW. A. LinkIndividual covariation in life-history traits: Seeing the trees despite the forest
We investigated the influence of age on survival and breeding rates in a long-lived species Rissa tridactyla using models with individual random effects permitting variation and covariation in fitness components among individuals. Differences in survival or breeding probabilities among individuals are substantial, and there was positive covariation between survival and breeding probability; birdsAuthorsE. Cam, W. A. Link, E.G. Cooch, J. -Y. Monnat, E. DanchinModel-based estimation of individual fitness
Fitness is the currency of natural selection, a measure of the propagation rate of genotypes into future generations. Its various definitions have the common feature that they are functions of survival and fertility rates. At the individual level, the operative level for natural selection, these rates must be understood as latent features, genetically determined propensities existing at birth. ThiAuthorsWilliam A. Link, Evan G. Cooch, Emmanuelle CamUsing Christmas Bird Count data in analysis of population change
The scientific credibility of Christmas Bird Count (CBC) results depend on the development and implementation of appropriate methods of statistical analysis. The key to any successful analysis of CBC data is to begin with a careful review of how the limitations of the data are likely to influence the results of the analysis, then to choose methods of analysis that accommodate as much as possibleAuthorsJ.R. Sauer, W. A. LinkHierarchical modeling of population stability and species group attributes from survey data
Many ecological studies require analysis of collections of estimates. For example, population change is routinely estimated for many species from surveys such as the North American Breeding Bird Survey (BBS), and the species are grouped and used in comparative analyses. We developed a hierarchical model for estimation of group attributes from a collection of estimates of population trend. TheAuthorsJ.R. Sauer, W. A. LinkRandom effects and shrinkage estimation in capture-recapture models
We discuss the analysis of random effects in capture-recapture models, and outline Bayesian and frequentists approaches to their analysis. Under a normal model, random effects estimators derived from Bayesian or frequentist considerations have a common form as shrinkage estimators. We discuss some of the difficulties of analysing random effects using traditional methods, and argue that a BayesiaAuthorsJ. Andrew Royle, W. A. Link