Survey Design And Statistical Methods For The Estimation Of Avian Population Trends

Proceedings of a workshop on the analysis of avian population trends, held April 1988 in Laurel, Maryland. Describes the design of major avian surveys, presents major analytical methods used to estimate population trends, and provides analyses of scissor-tailed flycatcher data set.

Wild birds are counted for a wide variety of reasons and by a bewildering array of methods. However, detailed descriptions of the techniques used and the rationale adopted are scattered in the literature, and the newcomer to bird census work or the experienced bird counter in search of a wider view, may well have difficulty in coming to grips with the subject as a whole. While not an end in itself, numerical and distributional census work is a fundamental part of many scientific and conservation studies, and one in which the application of given standards is vital if results are not to be distorted or applied in a misleading way. This book provides a concise guide to the various census techniques and to the opportunities and pitfalls which each entails. The common methods are described in detail, and illustrated through an abundance of diagrams showing examples of actual and theoretical census studies. Anyone with a bird census job to plan should be able to select the method best suited to the study at hand, and to apply it to best effect within the limits inherent in it and the constraints of the particular study. The Royal Society for the Protection of Birds and the British Trust for Ornithology have for many years pioneered the collaboration of amateurs and professionals in various census studies. Three members of their staff, each with extensive field experience, now pool the knowledge of these investigations to lay the groundwork for sound census work in future years.

Point counts of birds are the most widely used quantitative method and involve an observer recording birds from a single point for a standardized time period. In response to the need for standardization of methods to monitor bird populations by census, researchers met to present data from various investigations working under a wide variety of conditions, and to examine various aspects of point count methodology. Statistical aspects of sampling and analysis were discussed and applied to the objectives of point counts. The final chapter presents these standards and their applications to point count methodology.