Advances in ECOLOGICAL RESEARCH VOLUME 8 A This Page Intentionally Left Blank Advances in ECOLOGICAL RESEARCH Edited by A. MACFADYEN School of Biological and Environmental Studies, New University of Ulster, Coleraine, County Londonderry, Northern Ireland VOLUME 8 1974 ACADEMIC PRESS London and New York A Subsidiary of Harcourt Brace Jovanovich, Publishers ACADEMIC PRESS INC. (LONDON) LTD 24/28 Oval Road London NW1 United States Edition published by ACADEMIC PRESS INC. 11 1 Fifth Avenue New York, New York 10003 Copyright @ 1974 by ACADEMIC PRESS INC. (LONDON) LTD. All Rights Reserved No part of this book may be reproduced in any form by photostat, microfilin or any other means, without written permission from the publishers Library of Congress Catalog Card Number: 62-21479 ISBN: 0-12-013908-1 PRINTED I N GREAT BRITAIN B Y T. AND A. CONSTABLE LTD., EDINBURGH Contributors to Volume 8 C. J. KREBS,Institute of Animal Resource Ecology, University of British Columbia, Vancouver, Canada. J. H. MYERS, Institute of Animal Resource Ecology, University of British Columbia, Vancouver, Canada. G. R. POTTS, Game Conservancy, Partridge Survival Project, North Farm, Washington, Pulborough, West Sussex, England. W. STREIFER, Xerox Palo Alto Research Center, 3180 Porter Drive, Palo Alto, California 94304, USA. G. P. VICKERMAN, Game Conservancy, Partridge Survival Project, North Farm, Washington, Pulborough, West Sussex, England. L. YOUNG,Washington State University, Pullman, Washington, USA. This Page Intentionally Left Blank Preface The ecologist today is faced with two major difficulties of communication, one fundamental to the science and the other concerningrelations with his fellow men. The fundamental difficulty is that of combining a broad understanding of complicated ecosystems with an accurate account of detail. This dilemma, faced by all scientists and reporters of science, is well described by Viza (1973)* in introducing a new journal on “Differentiation”: “The difficulty starts when one wants a synthetic view, to plan the key experiments and collect the relevant papers. If one of the dangers of this approach is over-generalization and simplification the converse is also common: focusing the experimental approach on a very restricted area, and, at the end of the exercise, losing its object, which becomes entangled in a complexity of details. . . . ” This problem is, in itself, sufficient justification for publications which allow an author scope to elaborate general principles and support them with accurate data and careful reasoning. The second problem, of communication with a wider audience, is currently affected by public awareness of the human relevance of ecological problems. It is influenced by the demand for “relevant” ecological research and speedy answers to practical problems. We now h d widely circulated “ecological” journals atacking the academic ecologist for obscurantism and irrelevance, frequently using as examples themes whose “relevance” was first detected by the very victims of these attacks! It is tempting, but unhelpful, to respond angrily. Nevertheless, some of the criticism is justified: there has been unimaginative, timeeerving, ecological research motivated neither by a search for scientific understanding nor for practical results. The training of few ecologists is broad enough to encompass the whole of ecology and we often have difficulties in appreciating the significance of work in an unfamiliar field.We all require continual re-education in this rapidly expanding field. These are the primary justihations for a publication such as the present, and these same reasons provide the criteria for acceptable review articles. I n terms of scope we should aim to cover a wide field extending int