Expedition Field Techniques BIRD SURVEYS Colin Bibby, Martin Jones and Stuart Marsden Together for birds and people Published by BirdLife International Wellbrook Court Girton Road Cambridge CB3 0NA Tel +44 (0)1223 277318 Fax +44 (0)1223 277200 Email: [email protected] Website www.birdlife.net March 2000 BirdLife International is a global conservation federation with a worldwide network of Partner organisations, Representatives and committed individuals. BirdLife International seeks to conserve all bird species on earth and their habitats and through this, it works for the world's biological diversity. It recognises that the problems affecting birds, their habitats and our global environment are linked inseparably with social, economic and cultural factors and that these can only be resolved if human societies function in an ecologically sustainable manner and if the needs, welfare and aspirations of people form a part of all conservation action. Birds provide BirdLife International with a uniquely valuable focus: they are sensitive indicators of biological richness and environmental trends and fulfil many key ecological functions; they contribute to our understanding of natural processes; they are an important economic resource; and they have inspired and delighted people of many cultures for centuries, which makes them excellent ambassadors for the promotion of conservation awareness and international collaboration. BirdLife International pursues a programme of: · Scientific research and analysis to identify and monitor worldwide the most threatened bird species and the most critical sites for the conservation of avian diversity; · Advocacy and policy development to promote the conservation of birds and biodiversity through sustainability in the use of all natural resources; · Field action and country conservation programmes, ranging from community-based land-use and management projects to species recovery programmes benefiting both wildlife and humans; · Network and capacity building to expand and strengthen the global partnership of conservation organisations and to promote worldwide the conservation of birds and the wider environment. Expedition Field Techniques BIRD SURVEYS CONTENTS Acknowledgements 1 Foreword 2 Introduction 3 Section One: Why Count Birds? 1.1 Species 5 1.2 Sites 7 1.3 Important Bird Areas 8 1.4 Habitats 10 1.5 Choice of methods 11 Section Two: Study Design 2.1 Introduction 15 2.1.1 Total counts 15 2.1.2 Sampling and bias 15 2.1.3 Sampling, precision and accuracy 16 2.1.4 Relative and absolute estimates 17 2.1.5 Measuring and increasing precision 18 2.2 Study Design 19 2.2.1 Choosing the right time and conditions 19 2.2.2 Observer bias 21 2.2.3 Sample sizes and replication 24 2.2.4 Positioning your sampling effort 26 2.3 Pilot surveys and training 29 2.4 Safety, team size and logistics 31 2.4.1 Health and safety 31 2.4.2 Logistics 31 2.4.3 What size team? 31 2.5 Which methods to use 32 2.5.1 Introduction 32 2.5.2 Bird densities 33 2.5.3 Point counts and line transects 34 Section Three: Estimating bird densities using distance sampling 3.1 Introduction 35 3.2 Distance sampling using line transects 36 3.2.1 Introduction 36 3.2.2 Positioning of transects 36 3.2.3 How many transects and how long should they be? 37 3.2.4 Collection of data 37 3.2.5 Double counting 40 3.2.6 Variable distances and distance bands 40 3.2.7 Distance estimations to groups 41 3.2.8 Sample sizes 41 3.3 Distance sampling using point counts 41 3.3.1 Introduction 41 3.3.2 Location of census stations 42 3.3.3 How many census stations? 43 3.3.4 How long should the count period be? 43 3.3.5 Data collection 43 3.3.6 Variable distances and distance bands 44 3.3.7 Sample sizes 45 3.4 Examining the data 45 3.4.1 Bird detectability and the detection curve 45 3.4.2 Shape criteria 47 3.5 Using the DISTANCE software 50 3.5.1 The basic model 50 3.5.2 Alternative models 50 3.5.3 Testing model fit 51 3.5.4 Inputting data 51 3.5.5 Understanding the output 52 Section Four: Counting single-species 4.1 Is a single-species study appropriate? 53 4.2 Narrowing down the search: information is the key 53 4.3 The nature of the beast: rarity 57 4.4 Problem species and difficult habitats 60 4.4.1 Bird colonies/aggregations 60 4.4.2 Cryptic and understorey birds 61 4.4.3 Canopy species 61 4.4.4 Mixed-species flocks 62 4.4.5 ‘Aerial’ birds 62 4.4.6 Nocturnal and crepuscular birds 62 Bird Surveys 4.4.7 Other ‘problem’ birds (waterbirds, birds of prey, migrants, etc.) 63 4.4.8 Special habitats/niches 63 4.5 Tailoring distance sampling methods for individual situations 64 4.6 Specific techniques for special cases 67 4.6.1 Spot mapping 67 4.6.2 Counting birds at or near aggregations 68 4.6.3 ‘Look down’ methods from vantage points 70 4.6.4 Nest searching/counting limited resources 71 4.6.5 Interviews with local people 73 4.6.6 Mark-recapture/banding/home ranges 73 4.6.7 Scientific birding 74 4.7 Interpreting and presenting results of specific studies 75 Section Five: Assessment of sites: measurement of species richness and diversity 5.1 Introduction 76 5.2 Compiling a species list 76 5.3 Standardising recording methods 81 5.3.1 Species discovery curves 81 5.3.2 Encounter rates 83 5.3.3 Mackinnon lists 84 5.3.4 Timed species-counts (TSCs) 86 5.3.5 Mist-netting 86 5.4 Analysis of data 87 5.4.1 Predicting total number of species from species discovery curves 87 5.4.2 Analysis of encounter rate data 89 5.4.3 Analysis of Mackinnon list data 91 5.4.4 Analysis of TSC data 91 5.4.5 Analysis of mist-net data 92 5.5 Discussion 94 5.6 Sources of information for the recording of bird sounds 97 Section Six: Bird-habitat studies 6.1 Why study habitats? 99 6.2 Broad scale habitat studies 100 6.2.1 What features to map? 100 6.2.2 Sources of data for mapping 101 6.2.3 Verification of a map and sampling 102 Bird Surveys 6.3 Fine scale bird-habitat studies 102 6.3.1 Different approaches/survey designs 102 6.3.2 What habitat features to record and how? 103 6.3.3 Preparation of data for analysis 108 6.4 Analytical approaches 110 6.4.1 Summary statistics 110 6.4.2 Indices 110 6.4.3 Graphical and linear regression approaches 111 6.4.4 Logistic regression 113 6.4.5 Reducing the dimensions 113 6.4.6 Interpreting and testing the results 114 Section Seven: Maximising the impact of the work 7.1 Basic communications 115 7.2 Culture, politics and diplomacy 116 7.3 Summary reporting 118 7.4 Scientific reporting 122 7.5 Archiving the data 124 Section Eight: References and further reading 125 Section Nine: Sample input and output files for DISTANCE Program 127 The BP Conservation Programme 134 Bird Surveys Acknowledgements This book is a collaborative effort. It was first published in English by the Expedition Advisory Centre of the Royal Geographical Society (with IBG). The free availability of the entire book on the world wide web has been made possible by the BP Conservation Programme. Thanks are due to authors of individual sections who additionally contributed to discussions about the whole project and on sections other than their own. We are particularly grateful to the following who read and helpfully criticised large parts of the text, bringing to bear their experience from around the world: Rod Hay, Sam Kanyamibwa, Borja Mila, Michael Poulsen, Richard Thomas and Hazell Thompson. Individual sections have benefited from the input of the following: Leon Bennun, S. Buckland (for technical help with DISTANCE), Paul Dolman, Bill Sutherland, David Whitacre and Rob Williams. Ian Burfield, John Pilgrim and Rob Williams helped in many ways in co- ordinating and bringing the project to fruition. Katharine Gotto from the BP Conservation Programme helped and encouraged throughout. We appreciate the help of Shane Winser and Timothy Jones at the Expedition Advisory Centre of the Royal Geographical Society for overseeing the final production process of the English paper version. Financial support from BP Amoco has allowed BirdLife International to distribute the book widely and publish it in Spanish and Indonesian. Author Profiles: Colin Bibby is the director of Science and Policy at BirdLife International’s UK headquarters. His interests are in the collection and use of scientific information for the conservation of birds and their habitats. Martin Jones is a senior lecturer in the Behavioural and Environmental Biology Group in the Department of Biological Sciences at Manchester Metropolitan University. His research interests are the ecology and conservation of tropical birds and the effects of habitat change on island birds and butterflies. Stuart Marsden is a lecturer in Behavioural and Environmental Biology in the Department of Biological Sciences at Manchester Metropolitan University. His main research interests are in the ecology and conservation of parrots and other tropical birds. *Figure 24 has been kindly reproduced with the permission of Oxford University Press. Taken from: Mackinnon, J. and Phillips, K. (1993) A Field Guide to the Birds of Sumatra, Java and Bali. Bird Surveys FOREWORD This book is a vital tool for everyone wishing to contribute to our knowledge of the world's birds and to bird conservation.