David N. Nettleship & David C. Duffy (eds) 1995.
THE DOUBLE-CRESTED CORMORANT: BIOLOGY, CONSERVATION AND MANAGEMENT.
Colonial Waterbirds 18, Special Publication 1. 256 pp.

At about the same time that European cormorant specialists joined their efforts in a special issue of the Dutch journal ARDEA, dedicated to Great Cormorant population development, ecology and identification of conflicts with human (fisheries’) interests (Van Eerden et al. 1995), the North American journal COLONIAL WATERBIRDS has published the proceedings and findings of a symposium on "The Double-crested Cormorant: Biology, Conservation and Management", held as part of the Colonial Waterbird Society Annual Meeting at the University of Mississippi, Oxford, Mississippi (USA) in autumn 1992. It is quite remarkable that two such similar initiatives, inspired by rather similar phenomena (a spectacular population increase of a versatile fish-eating waterbird, giving rise to concern among human fisheries’ interests), should occur at very much the same time, without the one group being aware of the activities of the other and yet produce two volumes that approach many of the pending issues from quite distinct angles. Therefore, the reader with a keen interest in fish-eating birds, their ecology and their potentials for getting mixed up with human interests will probably be able to browse through both these publications without too many déja vu experiences. On the other hand, for at least some of the more similar papers it seems a pity that no cross-references could be made to each other.

After a general introduction by both editors on "Cormorants and Human Interactions", the 27 main papers are divided among four parts. Part One "The Bird and the Problem" identifies the causes of the currently emerging conflicts in North America, e.g. the overall increase of the Double-crested Cormorant population throughout the United States and Canada, some general observations on cormorant ecology and human sociology with respect to pest wildlife species and a thorough description of the incidence of and developments in aquaculture in North America, this being the sector where the predatory habits of cormorants on fish are likely to have the severest economical impacts. Part Two "Regional Distribution, Status, and Conflicts" provides a series of 19 case studies from various areas and on a number of different topics, varying between regional compilations and analyses of the development in breeding bird numbers (often in combination with data on reproductive success), via evaluation of the effects of toxic chemicals and biometrical means to distinguish the sexes (at least in the hand) to case studies in which actual local problems are described and quantified, or even local solutions to these problems are proposed and evaluated. This section constitutes the most basic, but at the same time most diverse information, ranging from how to sex Double-crested Cormorants in the hand by biometric data via food habits of wintering birds to suggestions for techniques to prevent damage at aquaculture facilities.

Evidently, the scope of the COLONIAL WATERBIRDS special issue on cormorants and their problems has been slightly less biological and more applied than that of ARDEA's publication. Hardly any attention has been given to the reasons for the dramatic increase in recent years or to the natural factors responsible for population regulation. This is at least partly due to the fact that no long-term studies on breeding biology and/or population dynamics and hardly any studies on (natural) cormorant diets have ever been carried out, let alone, presented here. On the other hand, practical problems have been pinpointed rather more accurately and, although direct proof of economical damage even in aquaculture facilities is still lacking (particularly in the opinion of the 'cormorant scientists'), some suggestions are made on how to cope with the problem, either scaring off the birds or protecting the installations from depredation. It did not become clear, however, whether these control measures were actually effective, particularly if considered on system scale. The general conclusion was that much information needed for rational management of both aquaculture fish stocks and cormorants is still lacking and therefore a series of research recommendations was made. It is hopefully not only the economical damage inflicted by Double-crested Cormorants which would justify major scientific research in the near future. The biological processes for the parallel developments in populations of Ph. auritus and Ph. carbo on either side of the Atlantic needs further understanding and combination of information available could lead to successful measures aimed at a reduction in the damage to human fisheries. The editors are to be congratulated with the appearance of this issue!

Contents

Introduction

- Cormorants and Human Interactions: An Introduction. D.N. Nettleship & D.C. Duffy

Part One. The Bird and the Problem

- Changing Populations of Double-crested Cormorants. J.J. Hatch

- Why is the Double-crested Cormorant a problem? Insights from Cormorant Ecology and Human Sociology. D.C. Duffy

- Aquaculture and Birds: The Context for Controversy. I.M. Price & J.G. Nickum

Part Two. Regional Distribution, Status, and Conflicts

- Double-crested Cormorants of the Great Lakes: Changes in Population Size, Breeding Distribution and Reproductive Output between 1913 and 1991. D.V. Weseloh, P.J. Ewins, J. Struger, P. Mineau, C.A. Bishop, S. Postupalsky & J.P. Ludwig

- Evaluation of the Effects of Toxic Chemicals in Great Lakes Cormorants: Has Causality been Established? J.P. Ludwig, H.J. Auman, D.V. Weseloh, G.A. Fox, J.P. Giesy & M.E. Ludwig

- Recent Changes in the Abundance and Distribution of the Double-crested Cormorant in the St. Lawrence river, Estuary and Gulf, Québec, 1978-1990. G. Chapdelaine & J. Bédard

- Double-crested Cormorant Culling in the St. Lawrence River Estuary. J. Bédard, A. Nadeau & M. Lepage

- Double-crested Cormorant Morphometry and Field Sexing in the St. Lawrence River Estuary. J. Bédard, A. Nadeau & M. Lepage

- Shouting at Shags: A Case Study of Cormorant Management in Nova Scotia. G.R. Milton, P.J. Austin-Smith & G.J. Farmer

- Double-crested Cormorants in New England: Population and Management Histories. W.B. Krohn, R.B. Allen, J.R. Moring & A.E. Hutchinson

- Double-crested Cormorants and Fisheries in Florida. K.E. Brugger

The Double-crested Cormorant in the South-Central United States: Habitat and Population Changes of a Feathered Pariah. J.A. Jackson & B.J.S. Jackson

- Double-crested Cormorants along the Upper Mississippi River. E.M. Kirsch

- Wintering Double-crested Cormorants in the Delta Region of Mississippi: Population Levels and their Impact on the Catfish Industry. J.F. Glahn & A.R. Stickley

- Locations and numbers of Double-crested Cormorants Using Winter Roosts in the Delta Region of Misssissippi. A.R. Aderman & E.P. Hill

- Daily Activity Budgets and Movements of Winter-roosting Double-crested Cormorants Determined by Biotelemetry in the Delta Region of Mississippi. D.T. King, J.F. Glahn & K.J. Andrews

- Food Habits of Double-crested Cormorants Wintering in the Delta Region of Mississippi. J.F. Glahn, P.J. Dixson, G.A. Littauer & R.B. McCoy

- The Impact of Double-crested Cormorants on the Mississippi Delta Catfish Industry: A Bioenergetics Model. J.F. Glahn & K.E. Brugger

- A Review of Techniques for Preventing Cormorant Depredations at Aquaculture Facilities in the Southeastern United States. D.F. Mott & F.L. Boyd

- Origin, Population Attributes, and Management Conflict Resolution for Double-crested Cormorants Wintering in Texas. B.C. Thompson, J.J. Campo & R.C. Telfair

- Population Size, Trends, and Conservation Problems of the Double-crested Cormorant on the Pacific Coast of North America. H.R. Carter, A.L. Sowls, M.S. Rodway, U.W. Wilson, R.W. Lowe, G.J. McChesney, F. Gress & D.W. Anderson

- Breeding Success of Double-crested Cormorants in the San Francisco Bay Area, California. L.E. Stenzel, H.R. Carter, R.P. Henderson, S.D. Emslie, M.J. Rauzon, G.W. Page & P.Y. O'Brien

Part Three. Management Responsibility and Policy

- Management Responsibilities and Policies for Cormorants: United States Fish and Wildlife Service. J.L. Trapp, T.J. Dwyer, J.J. Goggett & J.G. Nickum

- Cormorant Management and Responsibilities: United States Department of Agriculture. B.R. Acord

- Management Policies for Cormorants in Canada. J.A. Keith

Part Four. Conclusions and Recommendations

- The Ecology of Cormorants: Some Research Needs and Recommendations. R.M. Erwin

- Biology, Conservation and Management of the Double-crested Cormorant: Symposium Summary and Overview. I.C.T. Nisbet

Epilogue

- Epilogue: Cormorants, Humans and Symposium Process. D.N. Nettleship & D.C. Duffy

Anyone interested in obtaining a copy of this special issue of Colonial Waterbirds is advised to contact the editor-in-chief: Donald A. McCrimmon, Jr., Office of Research, 520 O'Dowd Hall, Oakland University, Rochester, Michigan 48309, USA (810-370-3222 voice; 810-370-4114 fax; Internet: mccrimmon@oakland.edu).

MP