William Link, Ph.D. (Former Employee)
Science and Products
Filter Total Items: 44
No results found.
Filter Total Items: 122
On the importance of controlling for effort in analysis of count survey data: Modeling population change from Christmas Bird Count data
Count survey data are commonly used for estimating temporal and spatial patterns of population change. Since count surveys are not censuses, counts can be influenced by 'nuisance factors' related to the probability of detecting animals but unrelated to the actual population size. The effects of systematic changes in these factors can be confounded with patterns of population change. Thus, valid
Authors
W. A. Link, J.R. Sauer
Unbiasedness
Unbiasedness is probably the best known criterion for evaluating the performance of estimators. This note describes unbiasedness, demonstrating various failings of the criterion. It is shown that unbiased estimators might not exist, or might not be unique; an example of a unique but clearly unacceptable unbiased estimator is given. It is shown that unbiased estimators are not translation invari
Authors
W. A. Link
Estimating relative abundance from count data
Much of the available information on large-scale patterns of animal abundance is based on count surveys. The data provided by such surveys are often influenced by nuisance factors affecting the numbers of animals counted, but unrelated to population size. Temporal and spatial patterns in nuisance factors may exist, causing simple summaries of countsto give a misleading view of patterns in populati
Authors
William A. Link, John R. Sauer
New approaches to the analysis of population trends in land birds: Comment
James et al. (1996, Ecology 77:13-27) used data from the North American Breeding Bird Survey (BBS) to examine geographic variability in patterns of population change for 26 species of wood warblers. They emphasized the importance of evaluating nonlinear patterns of change in bird populations, proposed LOESS-based non-parametric and semi-parametric analyses of BBS data, and contrasted their resul
Authors
William A. Link, John R. Sauer
Estimation of population trajectories from count data
Monitoring of changes in animal population size is rarely possible through complete censuses; frequently, the only feasible means of monitoring changes in population size is to use counts of animals obtained by skilled observers as indices to abundance. Analysis of changes in population size can be severely biased if factors related to the acquisition of data are not adequately controlled for. I
Authors
W. A. Link, J.R. Sauer
Empirical Bayes estimation of proportions with application to cowbird parasitism rates
Bayesian models provide a structure for studying collections of parameters such are considered in the investigation of communities, ecosystems, and landscapes. This structure allows for improved estimation of individual parameters by considering them in the context of a group of related parameters. Individual estimates are differntially adjusted toward in overall mean, with the magnitude of their
Authors
William A. Link, D. Caldwell Hahn
Extremes in ecology: Avoiding the misleading effects of sampling variation in summary analyses
Surveys such as the North American Breeding Bird Survey (BBS) produce large collections of parameter estimates. One's natural inclination when confronted with lists of parameter estimates is to look for the extreme values: in the BBS, these correspond to the species that appear to have the greatest changes in population size through time. Unfortunately, extreme estimates are liable to correspond t
Authors
William A. Link, John R. Sauer
The 1994 and 1995 summary of the North American Breeding Bird Survey
Data from the North American Breeding Bird Survey were used to estimate continental and regional changes in bird populations for the 2-year periods of 1993-1994 and 1994-1995. These 2-year changes were placed in the context of population trends estimated over the 1966-1995 interval. The 2-year changes were more positive during the 1993-1994 period, when 54.2% of all species exhibited positive co
Authors
B.G. Peterjohn, J.R. Sauer, W. A. Link
A resource conservative procedure for comparison of dose-response relationships
The evaluation of effects of toxicants on a wildlife community can be complicated by varying responses among the community's constituent populations. Even within populations, considerable variability in dose-response relations may result from different avenues of exposure to the toxicant. Full-scale investigations of the dose-response relations among a variety of species and avenues of exposure ca
Authors
W. A. Link, E. F. Hill, J. E. Hines, P.F.P. Henry
Coexistence and community structure of tropical trees in a Hawaiian montane rain forest
We measured the diameter at breast height of all trees and shrubs > 5 meters in height, including standing dead trees, on 68 0.04-hectare study plots in a montane, subtropical rain forest on Mauna Loa, Hawai`i. The canopy species consisted of 88 percent Metrosideros polymorpha (ohia) and 12 percent Acacia koa (koa). Negative associations were found between the densities of koa and ohia, the den
Authors
Jeff S. Hatfield, William A. Link, Deanna K. Dawson, E. L. Lindquist
Estimation and confidence intervals for empirical mixing distributions
Questions regarding collections of parameter estimates can frequently be expressed in terms of an empirical mixing distribution (EMD). This report discusses empirical Bayes estimation of an EMD, with emphasis on the construction of interval estimates. Estimation of the EMD is accomplished by substitution of estimates of prior parameters in the posterior mean of the EMD. This procedure is examin
Authors
W. A. Link, J.R. Sauer
Correcting for overdispersion in tests of prey selectivity
No abstract available.
Authors
W. A. Link, K. U. Karanth
Science and Products
Filter Total Items: 44
No results found.
Filter Total Items: 122
On the importance of controlling for effort in analysis of count survey data: Modeling population change from Christmas Bird Count data
Count survey data are commonly used for estimating temporal and spatial patterns of population change. Since count surveys are not censuses, counts can be influenced by 'nuisance factors' related to the probability of detecting animals but unrelated to the actual population size. The effects of systematic changes in these factors can be confounded with patterns of population change. Thus, valid
Authors
W. A. Link, J.R. Sauer
Unbiasedness
Unbiasedness is probably the best known criterion for evaluating the performance of estimators. This note describes unbiasedness, demonstrating various failings of the criterion. It is shown that unbiased estimators might not exist, or might not be unique; an example of a unique but clearly unacceptable unbiased estimator is given. It is shown that unbiased estimators are not translation invari
Authors
W. A. Link
Estimating relative abundance from count data
Much of the available information on large-scale patterns of animal abundance is based on count surveys. The data provided by such surveys are often influenced by nuisance factors affecting the numbers of animals counted, but unrelated to population size. Temporal and spatial patterns in nuisance factors may exist, causing simple summaries of countsto give a misleading view of patterns in populati
Authors
William A. Link, John R. Sauer
New approaches to the analysis of population trends in land birds: Comment
James et al. (1996, Ecology 77:13-27) used data from the North American Breeding Bird Survey (BBS) to examine geographic variability in patterns of population change for 26 species of wood warblers. They emphasized the importance of evaluating nonlinear patterns of change in bird populations, proposed LOESS-based non-parametric and semi-parametric analyses of BBS data, and contrasted their resul
Authors
William A. Link, John R. Sauer
Estimation of population trajectories from count data
Monitoring of changes in animal population size is rarely possible through complete censuses; frequently, the only feasible means of monitoring changes in population size is to use counts of animals obtained by skilled observers as indices to abundance. Analysis of changes in population size can be severely biased if factors related to the acquisition of data are not adequately controlled for. I
Authors
W. A. Link, J.R. Sauer
Empirical Bayes estimation of proportions with application to cowbird parasitism rates
Bayesian models provide a structure for studying collections of parameters such are considered in the investigation of communities, ecosystems, and landscapes. This structure allows for improved estimation of individual parameters by considering them in the context of a group of related parameters. Individual estimates are differntially adjusted toward in overall mean, with the magnitude of their
Authors
William A. Link, D. Caldwell Hahn
Extremes in ecology: Avoiding the misleading effects of sampling variation in summary analyses
Surveys such as the North American Breeding Bird Survey (BBS) produce large collections of parameter estimates. One's natural inclination when confronted with lists of parameter estimates is to look for the extreme values: in the BBS, these correspond to the species that appear to have the greatest changes in population size through time. Unfortunately, extreme estimates are liable to correspond t
Authors
William A. Link, John R. Sauer
The 1994 and 1995 summary of the North American Breeding Bird Survey
Data from the North American Breeding Bird Survey were used to estimate continental and regional changes in bird populations for the 2-year periods of 1993-1994 and 1994-1995. These 2-year changes were placed in the context of population trends estimated over the 1966-1995 interval. The 2-year changes were more positive during the 1993-1994 period, when 54.2% of all species exhibited positive co
Authors
B.G. Peterjohn, J.R. Sauer, W. A. Link
A resource conservative procedure for comparison of dose-response relationships
The evaluation of effects of toxicants on a wildlife community can be complicated by varying responses among the community's constituent populations. Even within populations, considerable variability in dose-response relations may result from different avenues of exposure to the toxicant. Full-scale investigations of the dose-response relations among a variety of species and avenues of exposure ca
Authors
W. A. Link, E. F. Hill, J. E. Hines, P.F.P. Henry
Coexistence and community structure of tropical trees in a Hawaiian montane rain forest
We measured the diameter at breast height of all trees and shrubs > 5 meters in height, including standing dead trees, on 68 0.04-hectare study plots in a montane, subtropical rain forest on Mauna Loa, Hawai`i. The canopy species consisted of 88 percent Metrosideros polymorpha (ohia) and 12 percent Acacia koa (koa). Negative associations were found between the densities of koa and ohia, the den
Authors
Jeff S. Hatfield, William A. Link, Deanna K. Dawson, E. L. Lindquist
Estimation and confidence intervals for empirical mixing distributions
Questions regarding collections of parameter estimates can frequently be expressed in terms of an empirical mixing distribution (EMD). This report discusses empirical Bayes estimation of an EMD, with emphasis on the construction of interval estimates. Estimation of the EMD is accomplished by substitution of estimates of prior parameters in the posterior mean of the EMD. This procedure is examin
Authors
W. A. Link, J.R. Sauer
Correcting for overdispersion in tests of prey selectivity
No abstract available.
Authors
W. A. Link, K. U. Karanth