William Link, Ph.D. (Former Employee)
Science and Products
Filter Total Items: 44
No results found.
Filter Total Items: 124
Hierarchical models and Bayesian analysis of bird survey information
Summary of bird survey information is a critical component of conservation activities, but often our summaries rely on statistical methods that do not accommodate the limitations of the information. Prioritization of species requires ranking and analysis of species by magnitude of population trend, but often magnitude of trend is a misleading measure of actual decline when trend is poorly estimat
Authors
J.R. Sauer, W. A. Link, J. Andrew Royle
Nonlinearity and seasonal bias in an index of brushtail possum abundance
Introduced brushtail possums (Trichosurus vulpecula) are a widespread pest of conservation and agriculture in New Zealand, and considerable effort has been expended controlling populations to low densities. A national protocol for monitoring the abundance of possums, termed trap catch index (TCI), was adopted in 1996. The TCI requires that lines of leghold traps set at 20-m spacing are randomly lo
Authors
David M. Forsyth, William A. Link, R. Webster, G. Nugent, B. Warburton
Modeling association among demographic parameters in analysis of open population capture-recapture data
We present a hierarchical extension of the Cormack–Jolly–Seber (CJS) model for open population capture–recapture data. In addition to recaptures of marked animals, we model first captures of animals and losses on capture. The parameter set includes capture probabilities, survival rates, and birth rates. The survival rates and birth rates are treated as a random sample from a bivariate distribution
Authors
William A. Link, Richard J. Barker
A general class of multinomial mixture models for anuran calling survey data
We propose a general framework for modeling anuran abundance using data collected from commonly used calling surveys. The data generated from calling surveys are indices of calling intensity (vocalization of males) that do not have a precise link to actual population size and are sensitive to factors that influence anuran behavior. We formulate a model for calling-index data in terms of the maximu
Authors
J. Andrew Royle, William A. Link
Using the North American Breeding Bird Survey as a tool for conservation: A critique of Bart et al. (2004)
Bart et al. (2004) develop methods for predicting needed samples for estimation of long-term trends from Count survey data, and they apply these methods to the North American Breeding Bird Survey (BBS). They recommend adding approximately 40% more survey routes ill the BBS to allow for estimation of long-term (i.e., 20 year) trends for a collection of species. We critique several aspects of thei
Authors
John R. Sauer, William A. Link, James D. Nichols, J. Andrew Royle
Quantifying production of salmon fry in an unscreened irrigation system: A case study on the Rangitata River, New Zealand
Diversion of out-migrant juvenile salmon into unscreened irrigation and hydroelectric canals is thought to have contributed significantly to declining populations of anadromous salmonids in the Pacific Northwest but is seldom studied in detail. Here we describe a program to study the fate of Chinook salmon Oncorhynchus tshawytscha fry diverted into the unscreened Rangitata Diversion Race (RDR) on
Authors
M. J. Unwin, M. Webb, R. J. Barker, William A. Link
Individual heterogeneity and identifiability in capture-recapture models
Individual heterogeneity in detection probabilities is a far more serious problem for capture-recapture modeling than has previously been recognized. In this note, I illustrate that population size is not an identifiable parameter under the general closed population mark-recapture model Mh. The problem of identifiability is obvious if the population includes individuals with pi = 0, but persists e
Authors
W. A. Link
Testing life history predictions in a long-lived seabird: A population matrix approach with improved parameter estimation
Life history theory and associated empirical generalizations predict that population growth rate (λ) in long-lived animals should be most sensitive to adult survival; the rates to which λ is most sensitive should be those with the smallest temporal variances; and stochastic environmental events should most affect the rates to which λ is least sensitive. To date, most analyses attempting to examine
Authors
P.F. Doherty, E.A. Schreiber, J. D. Nichols, J. E. Hines, W. A. Link, G.A. Schenk, R.W. Schreiber
Estimating population trends with a linear model: Technical comments
Controversy has sometimes arisen over whether there is a need to accommodate the limitations of survey design in estimating population change from the count data collected in bird surveys. Analyses of surveys such as the North American Breeding Bird Survey (BBS) can be quite complex; it is natural to ask if the complexity is necessary, or whether the statisticians have run amok. Bart et al. (200
Authors
John R. Sauer, William A. Link, J. Andrew Royle
Statistical analyses make the Christmas Bird Count relevant for conservation
No abstract available.
Authors
J.R. Sauer, W. A. Link, D.K. Niven
Some consequences of using counts of birds banded as indices to populations
In mist-net studies, it is often difficult to use capture-recapture methods to estimate number of birds present. Many investigators use number of birds captured as an index of population size. We investigate the consequences of using indices of bird abundance as surrogates for population size in hypothesis tests. Unless all of the birds present are captured, indices are biased estimates of loca
Authors
J.R. Sauer, W. A. Link
Christmas Bird Count provides insights into population change in land birds that breed in the boreal forest
No abstract available.
Authors
D.K. Niven, J.R. Sauer, G.S. Butcher, W. A. Link
Science and Products
Filter Total Items: 44
No results found.
Filter Total Items: 124
Hierarchical models and Bayesian analysis of bird survey information
Summary of bird survey information is a critical component of conservation activities, but often our summaries rely on statistical methods that do not accommodate the limitations of the information. Prioritization of species requires ranking and analysis of species by magnitude of population trend, but often magnitude of trend is a misleading measure of actual decline when trend is poorly estimat
Authors
J.R. Sauer, W. A. Link, J. Andrew Royle
Nonlinearity and seasonal bias in an index of brushtail possum abundance
Introduced brushtail possums (Trichosurus vulpecula) are a widespread pest of conservation and agriculture in New Zealand, and considerable effort has been expended controlling populations to low densities. A national protocol for monitoring the abundance of possums, termed trap catch index (TCI), was adopted in 1996. The TCI requires that lines of leghold traps set at 20-m spacing are randomly lo
Authors
David M. Forsyth, William A. Link, R. Webster, G. Nugent, B. Warburton
Modeling association among demographic parameters in analysis of open population capture-recapture data
We present a hierarchical extension of the Cormack–Jolly–Seber (CJS) model for open population capture–recapture data. In addition to recaptures of marked animals, we model first captures of animals and losses on capture. The parameter set includes capture probabilities, survival rates, and birth rates. The survival rates and birth rates are treated as a random sample from a bivariate distribution
Authors
William A. Link, Richard J. Barker
A general class of multinomial mixture models for anuran calling survey data
We propose a general framework for modeling anuran abundance using data collected from commonly used calling surveys. The data generated from calling surveys are indices of calling intensity (vocalization of males) that do not have a precise link to actual population size and are sensitive to factors that influence anuran behavior. We formulate a model for calling-index data in terms of the maximu
Authors
J. Andrew Royle, William A. Link
Using the North American Breeding Bird Survey as a tool for conservation: A critique of Bart et al. (2004)
Bart et al. (2004) develop methods for predicting needed samples for estimation of long-term trends from Count survey data, and they apply these methods to the North American Breeding Bird Survey (BBS). They recommend adding approximately 40% more survey routes ill the BBS to allow for estimation of long-term (i.e., 20 year) trends for a collection of species. We critique several aspects of thei
Authors
John R. Sauer, William A. Link, James D. Nichols, J. Andrew Royle
Quantifying production of salmon fry in an unscreened irrigation system: A case study on the Rangitata River, New Zealand
Diversion of out-migrant juvenile salmon into unscreened irrigation and hydroelectric canals is thought to have contributed significantly to declining populations of anadromous salmonids in the Pacific Northwest but is seldom studied in detail. Here we describe a program to study the fate of Chinook salmon Oncorhynchus tshawytscha fry diverted into the unscreened Rangitata Diversion Race (RDR) on
Authors
M. J. Unwin, M. Webb, R. J. Barker, William A. Link
Individual heterogeneity and identifiability in capture-recapture models
Individual heterogeneity in detection probabilities is a far more serious problem for capture-recapture modeling than has previously been recognized. In this note, I illustrate that population size is not an identifiable parameter under the general closed population mark-recapture model Mh. The problem of identifiability is obvious if the population includes individuals with pi = 0, but persists e
Authors
W. A. Link
Testing life history predictions in a long-lived seabird: A population matrix approach with improved parameter estimation
Life history theory and associated empirical generalizations predict that population growth rate (λ) in long-lived animals should be most sensitive to adult survival; the rates to which λ is most sensitive should be those with the smallest temporal variances; and stochastic environmental events should most affect the rates to which λ is least sensitive. To date, most analyses attempting to examine
Authors
P.F. Doherty, E.A. Schreiber, J. D. Nichols, J. E. Hines, W. A. Link, G.A. Schenk, R.W. Schreiber
Estimating population trends with a linear model: Technical comments
Controversy has sometimes arisen over whether there is a need to accommodate the limitations of survey design in estimating population change from the count data collected in bird surveys. Analyses of surveys such as the North American Breeding Bird Survey (BBS) can be quite complex; it is natural to ask if the complexity is necessary, or whether the statisticians have run amok. Bart et al. (200
Authors
John R. Sauer, William A. Link, J. Andrew Royle
Statistical analyses make the Christmas Bird Count relevant for conservation
No abstract available.
Authors
J.R. Sauer, W. A. Link, D.K. Niven
Some consequences of using counts of birds banded as indices to populations
In mist-net studies, it is often difficult to use capture-recapture methods to estimate number of birds present. Many investigators use number of birds captured as an index of population size. We investigate the consequences of using indices of bird abundance as surrogates for population size in hypothesis tests. Unless all of the birds present are captured, indices are biased estimates of loca
Authors
J.R. Sauer, W. A. Link
Christmas Bird Count provides insights into population change in land birds that breed in the boreal forest
No abstract available.
Authors
D.K. Niven, J.R. Sauer, G.S. Butcher, W. A. Link