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J.D. Nichols

Publications and source records attributed to J.D. Nichols.

At least 163 records · Page 9Linked to original sources
USGS1996

Introduction

Explore the source record for details and available documents.

Book chapter↗
USGS1996

The management of hunting of Anatidae

The objectives of harvest management for members of family Anatidae typically involve the size of the harvested population and the size of the harvest. Hunting regulations are the primary tool used to try to achieve the objectives of harvest management. Informed harvest management thus requires a knowledge of the relationship between hunting regulations and both Anatid abundance and harvest. Results of retrospective studies in North America provide evidence that generally restrictive regulations produce lower harvest rates than generally liberal regulations. However, such studies have provided little evidence that specific hunting regulations designed to produce a change in the relative harvest rates of different species, or of the sexes within a species, have been successful in 'directing' harvest toward specific groups of birds and away from other groups. Estimates of the strength of the relationship between harvest mortality rates and annual survival rates of Anatidae have ranged from weak to strong. Thus, the key relationships for harvest management of Anatidae, those between hunting regulations and the size of both the subsequent harvest and the subsequent population, are not 'known' but are characterized by uncertainty. In the United States, this uncertainty led to a risk-aversive conservatism that characterized the setting of hunting regulations during the last decade. Recently, managers have begun to consider using hunting regulations themselves as a means to better understand the system being managed. This approach, referred to as active adaptive management, attempts to balance short-term demands for hunting opportunity with the learning needed to improve long-term management performance. Learning is accomplished by periodically comparing observed system response, as estimated by ongoing survey and data collection programs, with predictions of competing models. These periodic comparisons lead to changes in measures of credibility associated with the different models and thus to a reduction in uncertainty. We suggest that this approach might be useful in other countries that have implemented requisite data collection programs for their Anatid populations.

Book chapter↗
USGS1995

On the use of secondary capture-recapture samples to estimate temporary emigration and breeding proportions

The use of the Cormack- Jolly-Seber model under a standard sampling scheme of one sample per time period, when the Jolly-Seber assumption that all emigration is permanent does not hold, leads to the confounding of temporary emigration probabilities with capture probabilities. This biases the estimates of capture probability when temporary emigration is a completely random process, and both capture and survival probabilities when there is a temporary trap response in temporary emigration, or it is Markovian. The use of secondary capture samples over a shorter interval within each period, during which the population is assumed to be closed (Pollock's robust design), provides a second source of information on capture probabilities. This solves the confounding problem, and thus temporary emigration probabilities can be estimated. This process can be accomplished in an ad hoc fashion for completely random temporary emigration and to some extent in the temporary trap response case, but modelling the complete sampling process provides more flexibility and permits direct estimation of variances. For the case of Markovian temporary emigration, a full likelihood is required.

Book chapter↗
USGS1994

On the importance of sampling variance to investigations of temporal variation in animal population size

Our purpose here is to emphasize the need to properly deal with sampling variance when studying population variability and to present a means of doing so. We present an estimator for temporal variance of population size for the general case in which there are both sampling variances and covariances associated with estimates of population size. We illustrate the estimation approach with a series of population size estimates for black-capped chickadees (Parus atricapillus) wintering in a Connecticut study area and with a series of population size estimates for breeding populations of ducks in southwestern Manitoba.

Oikos↗
USGS1994

Sources of variation in loss rates of color bands applied to adult roseate terns ( Sterna dougallii ) in the western North Atlantic

A model-based analysis was done to test several hypotheses concerning the rates of loss of butt-ended color bands placed on adult Roseate Terns ( Sterna dougallii ) in the western North Atlantic. These birds were captured and color banded from 1987-1991 at four colony sites, and recaptured from 1989-1992 as part of a study of the population dynamics of this species. Two types of color bands, Darvic and celluloid, were used, but only one band type was used for each individual bird. Each bird was given three color bands. The estimated probability that a bird with all color bands present during one breeding season still had all color bands during the next breeding season was 0.87. The analysis provided no evidence that colony site, cohort, calendar year of banding, age of color band, or whether or not the bands were heat-sealed closed, were important sources of variation in band-retention probabilities.

The Auk↗
USGS1993

The estimation of exchanges among populations or subpopulations

Capture-recapture methods for estimating rates of immigration, emigration, and movement among geographic strata are reviewed. We discuss likelihood-based estimation methods under models incorporating Markovian and non-Markovian movement. We briefly describe a computer program developed by Brownie et al. (1992) to carry out the necessary estimation and testing.

Book chapter↗
USGS1993

Survival rate estimation in the presence of tag loss using joint analysis of capture-recapture and resighting data

Studies using resightings of marked birds typically make use of readily-observable tags that are not retained as well as metal legbands. We review methods for estimating survival rate with open capture-recapture / resighting models when tag loss is not negligible. All methods rely on data from double-banding studies, usually carried out as part of the resighting study by application of metal legbands to all birds marked with alternative markers. When tag loss is homogeneous, the methods of Arnason and Mills (1981) and Pollock (1981) can be used. When rates of tag loss depend on time since marking, then a cohort approach can be used and is similar to the methods appropriate for homogeneous tag loss. In addition, Kremers (1987) and Nichols et al. (1992) developed models for the joint analysis of recapture and resighting data in the presence of tag loss. We emphasize the importance of obtaining recapture data in observation-based studies in which tag loss is likely to be a problem. We discuss the allocation of effort to recaptures and resightings for such studies.

Book chapter↗