HERONS, EGRETS AND BITTERNS Their biology and conservation in Australia Neil McKilligan © Neil McKilligan 2005 All rights reserved. Except under the conditions described in the Australian Copyright Act 1968 and subsequent amendments, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, duplicating or otherwise, without the prior permission of the copyright owner. Contact CSIRO PUBLISHING for all permission requests. National Library of Australia Cataloguing-in-Publication entry McKilligan, Neil, 1940- . Herons, egrets and bitterns. Bibliography. ISBN 0 643 09133 5 (paperback). ISBN 0 643 09209 9 (netLibrary eBook). 1. Ardeidae – Australia. 2. Herons – Australia. 3. Egrets – Australia. 4. Bitterns – Australia. I. CSIRO Publishing. II. Title. 598.34 Available from CSIRO PUBLISHING 150 Oxford Street (PO Box 1139) Collingwood VIC 3066 Australia Telephone: +61 3 9662 7666 Local call: 1300 788 000 (Australia only) Fax: +61 3 9662 7555 Email: [email protected] Web site: www.publish.csiro.au Front cover Intermediate Egret, photo by Neil McKilligan Back cover Striated Heron, photo by John Moverly Set in Sabon 10.5/14pt Cover and text design by James Kelly Typeset by Paul Dickenson Printed in Australia by Ligare Contents Preface and acknowledgements v Introduction vii 1 Herons of the world 1 2 What makes herons different? 7 3 The importance of herons 17 4 Distribution, movements and longevity 23 5 Feeding and food 33 6 Breeding 43 7 Population numbers and conservation 65 Colour plates 79–86 8 Species resident in Australia 87 Cattle Egret 88 White-necked Heron 94 Great-billed Heron 96 Great Egret 98 Pied Heron 100 Intermediate Egret 102 White-faced Heron 104 Little Egret 106 Eastern Reef Egret 108 Striated Heron 110 Nankeen Night Heron 112 Little Bittern 115 Black Bittern 117 Australasian Bittern 119 9 Occasional visitors 121 Black-crowned Night Heron 121 Malayan Night Heron 122 Yellow Bittern 123 Cinnamon Bittern 123 Schrenk’s Bittern 124 Grey Heron 125 References 127 Index 132 To my family Preface and acknowledgments The aim of this book is to make Australian herons, egrets and bitterns better understood and more appreciated by bird watchers, students and indeed anyone who has a particular admiration for these striking members of our avian fauna and a concern for their long-term survival. Unless otherwise indicated, in what follows ‘heron’ will collectively refer to all three of these members of the family Ardeidae. This book is certainly overdue. In fact, it is more than 30 years since, at the first campout of the Queensland Ornithological Society (now Birds Queensland), Dr Doug Dow alerted me to the need for monographs on Australian bird families. Since then some excellent field guides and beautifully illustrated bird books have been published and there is a wealth of detailed tech- nical information on many of our bird species in the volumes of the Handbook of Australian, New Zealand and Antarctic Birds (HANZAB) (Marchant and Higgins 1990 and subsequent authors). However, there is still a dearth of books that focus on families of Australian birds with the aim of making the facts and principles of their biology and conservation accessible to a wide readership. It seems the germ of the idea of writing such a book lay dormant in my mind all these years, but now, after decades of research into the Cattle Egret and shorter forays into the field studying other species of herons, I feel I have sufficient depth and breadth of knowledge to be comfortable with the idea of producing a book that looks comprehensively at the Australian members of the family Ardeidae. Nevertheless I am very conscious of my limited field experience of many of our ardeids and gratefully make use of what others have published and told me, while accepting the reality that a number of our heron species have hardly been studied at all. The book starts with worldwide and Australian perspectives on the heron family, outlining the herons’ habits and habitats, origin and biogeography, classification and relationships. It then describes their distinctive physical char- acteristics, and their importance to humans. It goes on to compare and contrast aspects of the biology of Australian herons, looking at their distribu- tion and movements, feeding and breeding. It reviews species numbers, the loss of much habitat and the need to protect, enhance and indeed restore shallow wetlands. Finally a separate ‘thumbnail sketch’ is given for each of the 14 heron species resident in Australia and briefer accounts of the six species that are very occasional visitors to Australian territory. vi Herons, egrets and bittterns A good deal of general biology can be learnt through the study of birds and the opportunity is also taken here to expand on certain topics as they relate to herons. Recognising that some of these topics will be familiar to some readers I’ve included them as separate ‘boxes’ so they don’t disrupt the flow of the main text and may be read at your leisure. My wish is that this book should be read with enjoyment and lead the reader to more satisfying ‘heron-watching’. Also that the challenges of preserv- ing heron habitats will be better understood and pursued more vigorously. Finally, it would be excellent if this book encouraged bird enthusiasts to undertake research on the ardeids, especially on those species whose biology is presently poorly understood. Inevitably a book of this sort draws on the work of many people. I have accessed this mostly through conventional literature searches, but where I have made direct requests to researchers I have been very thankful for the speed and helpfulness of their replies. The Australian Bird and Bat Banding Scheme provided heron recovery data that gives banding and recovery locations, distance travelled and age of death. I am especially appreciative of the comments on a draft of the text made by Greg Baxter, Roger Jaensch, Max Maddock and Harry Recher, whose research has given them a different perspective on these birds from my own. The book is also greatly enhanced by the use of illustrations from The New Atlas of Australian Birds (Barrett et al. 2003) and Waterbird Breeding Colonies in the Top End of the Northern Territory (Chatto 2000). Closer to home, I must thank the University of Southern Queensland and especially the technical staff, past and present, in biology, computing and media services for their support over many years. Thanks also to the many local naturalists and bird watchers who have performed a sterling service by counting egret nests in Lockyer Valley (south-east Queensland) swamps year after year. Birds Queensland kindly provided heron images from their slide library and my request to use these met with universal agreement from the photographers. Regrettably I could not use all of their very high-quality slides. Nick Alexander and his staff at CSIRO Publishing have very efficiently executed the technical processes, largely a mystery to me, needed to bring this project to fruition. Carol Stephens drew some very nice line drawings and last but by no means least, my wife Helen has always been there for me, encourag- ing and actively supporting my efforts. Introduction ome of our herons are very familiar to us. They are large, elegant, eye-catch- Sing birds that are easily observed as they feed in open landscapes or aggre- gate in large colonies for roosting and nesting. Others, however, are secretive in their habits, preferring the cover of reed beds and other dense vegetation on the edges of lakes, rivers and estuaries, and live a more solitary existence. From a narrow, utilitarian point of view herons might seem to be of little value to humans, with the probable exception of the Cattle Egret that eats Cattle Ticks and large numbers of grass-eating insects. Their flesh feeds very few people (if any), their feathers are no longer a fashion item and they are not known to be an important source of medicines. Nor are their wastes (guano) easily harvested for fertiliser, as is the case with some colonial seabirds. Some fish farmers see them as pests when they raid their ponds, although their economic impact tends to be exaggerated. On deeper consideration, however, it is apparent that herons can make a large contribution to the quality of human lives in a variety of ways. Their beauty inspires artists and charms ordinary folk. The presence of different heron species in a wetland gives us an immediate insight into its biodiversity. Herons may also be bioindicators, in the sense of revealing the presence of toxic materials in their habitats. This is because, as top predators, certain pollutants may concentrate in their bodies causing death or illness or low breeding success. Consequently a study of a heron population could give early warning of problems that, if not checked, would eventually impact on human health. Conservation of our natural wetlands is synonymous with the conserva- tion of many heron species but not any water-body will do. They must have shallow water, as virtually all herons that feed in water are restricted to wading in order to find their prey. The wading depth is limited by the length of the bird’s lower leg so potential prey in water deeper than 20–30 cm (depend- ing on the size of the bird) is not accessible to wading birds. Exceptions do occur and remarkably, quite a few heron species, including the Great Egret, have been observed diving off a perch into deep water to catch a fish (H. Recher, pers. comm.). Wetlands used by heron species include freshwater marshes and the margins of lakes and rivers, estuaries and coral reefs.