Bat roosts in trees : a guide to identification and assessment for tree-care and ecology professionals

This is a guide to finding tree-roosts. It is the result of the collaborative efforts of professional surveyors and amateur naturalists across Europe as part of the Bat Tree Habitat Key project, and represents a combination of firsts: It is the first time legislation and planning policy have been reviewed and put to practical use to define an analysis framework with clearly identifiable thresholds for action. Yet, despite its efficacy in a professional context, it is also the first time a guide has been produced that is equally effective in achieving its objective for amateurs. It is the first time such a method has been evidence-supported throughout, with summary reviews of each aspect of the roosting ecology of the individual 14 tree-roosting species, with illustrative photographs and data to which the reader has open access. It is the first time a repeatable analysis framework has been defined against which the surveyor may compare their results at every stage, from the desk-study, through ground-truthing, survey and analysis, thereby ensuring nothing is overlooked and that every result can be objectively compared. The survey and analysis framework itself is ground-breaking in that it may readily be adapted for any taxa; from moths, through amphibians, reptiles, birds and all other mammals. Used diligently, these methods will reward disproportionately and imbue the reader with renewed confidence as they quickly progress from beginner to competency. Thus, this book is for everyone who has ever wanted to find a tree-roost, or to safeguard against inadvertently damaging one. Bat Roosts in Trees: A Guide to Identification and Assessment for Tree-Care and Ecology Professionals Cover Page Title Page Copyright Contents Preface Citing, Credits and Acknowledgements Citing Credits Text Henry Andrews Mark Gardener Photographs Acknowledgements CHAPTER 1: Rationale 1.1 Introduction 1.2 Pre-existing published advice 1.3 Motivation 1.3.1 The law 1.4 Objective 1.5 PROPORTIONALITY CHAPTER 2: Tree-Roosting Bats 2.1 Tree-roosting bat species 2.2 Wooded habitat and tree species 2.2.1 Woodland 2.2.2 Plantation 2.2.3 Traditional orchard 2.2.4 Wooded linear landscape elements 2.2.5 Parkland 2.2.6 Churchyards and gardens 2.2.7 Sycamore 2.2.8 Summary 2.3 Sensitivity to isolation 2.4 Seasonal tree-roost occupancy and roost sizes 2.4.1 Seasons 2.4.2 Roost sizes 2.4.3 Mating 2.4.4 Summary 2.5 Roost heights 2.5.1 Winter 2.5.2 Spring-flux 2.5.3 Pregnancy 2.5.4 Nursery 2.5.5 Mating 2.5.6 Autumn-flux 2.5.7 Summary 2.6 General tree-roost preferences 2.6.1 Summing-up CHAPTER 3: Potential Roost Features (PRFs) 3.1 Introduction 3.2 The Disease & Decay PRFs 3.2.1 Introduction 3.2.2 Jim-Gem 3.2.3 Summary 3.3 The Damage PRFs 3.3.1 Ram’s-horns 3.3.2 Summary 3.4 The Association PRFs 3.4.1 Summary CHAPTER 4: Intelligence-Gathering 4.1 Introduction 4.2 Resources 4.2.1 The habitat map 4.2.2 The habitat description 4.2.3 The bat species inventory 4.2.4 The data-search 4.3 Collation of the results CHAPTER 5: The Desk-Study 5.1 Introduction 5.2 The desk-study objective 5.3 The test of “reasonable likelihood” 5.3.1 Rationale 5.4 To survey or not to survey? 5.4.1 Reality checkpoint CHAPTER 6: Ground-Truthing 6.1 Introduction 6.2 Ground-truthing method 6.2.1 Preparation 6.2.2 Timing 6.2.3 The operation 6.2.4 Equipment 6.3 Ground-truthing interpretation CHAPTER 7: Choosing the Surveillance Methods 7.1 Introduction 7.2 Close-inspection 7.2.1 Rationale 7.2.2 Strengths and weaknesses 7.3 Remote-observation 7.3.1 Rationale 7.3.2 Strengths and weaknesses 7.4 Static-netting 7.4.1 Rationale 7.4.2 Strengths and weaknesses 7.5 Radiotracking 7.5.1 Rationale 7.5.2 Strengths and weaknesses 7.6 Putting it all together 7.7 The proportionality test CHAPTER 8: Close-Inspection 8.1 Introduction 8.2 Equipment 8.2.1 The ground-truthing account 8.2.2 The BTHK recording form 8.2.3 The endoscope 8.3 Health and Safety 8.4 Close-inspection method 8.4.1 Constraints 8.4.2 Close-inspection: Stage 4 – Odour 8.4.3 Close-inspection: Stage 5 – Housekeeping 8.5 Interpretation 8.5.1 General 8.5.2 Presentation of inspection results 8.5.3 Interpretation steps 8.5.4 Positive encounters 8.5.5 Negative outcomes 8.5.6 Acceptance of omissions and shortfalls in the data 8.5.7 Summing-up CHAPTER 9: Remote-Observation 9.1 Introduction 9.2 Confounding factors 9.2.1 Bat ecology 9.2.2 Human biology 9.2.3 Wooded environments 9.2.4 The solution 9.3 Equipment 9.4 Health and Safety 9.5 Remote-observation method 9.5.1 Remote-observation: Stage 1 – Review 9.5.2 Remote-observation: Stage 2 – Assessing the conditions 9.5.3 Remote-observation: Stage 3 – Search for droppings 9.5.4 Remote-observation: Stage 4 – Set-up 9.5.5 Remote-observation: Stage 5 – Observation 9.6 Interpretation 9.6.1 Presentation of observation results 9.6.2 Droppings 9.6.3 Emergence, return and visitation 9.6.4 Investigation 9.6.5 Competitors 9.6.6 Summing-up CHAPTER 10: Static-Netting 10.1 Introduction 10.2 Equipment 10.3 Health and Safety 10.4 Static-netting method 10.4.1 Static-netting: Stage 1 – Review 10.4.2 Static-netting: Stage 2 – Assessing the conditions 10.4.3 Static-netting: Stage 3 – Search for droppings 10.4.4 Static-netting: Stage 4 – Set-up 10.4.5 Static-netting: Stage 5 – Netting 10.4.6 Static-netting: Stage 6 – Retrieval, handling, identification and release 10.5 Interpretation CHAPTER 11: Surveillance Effort 11.1 Introduction 11.2 Detectability variables 11.2.2 Distribution and abundance 11.2.3 Seasonal usage of trees 11.2.4 Activity 11.2.5 Sex 11.2.6 Duration of occupancy 11.3 Surveillance periods and intensity therein 11.3.1 General 11.3.2 Winter 11.3.3 Pregnancy 11.3.4 Nursery 11.3.5 Mating 11.3.6 Autumn-flux CHAPTER 12: Trouble-Shooting 12.1 Introduction 12.2 Fundamental principles 12.3 Inconclusive and ‘null’ results 12.3.1 Legislation: roosting bats 12.3.2 Pre-development site interest: roosting bats 12.4 Indirect damage and disturbance 12.4.1 Deliberate 12.4.2 Disturbance 12.5 Comparative assessment of environment (i.e. environmental impact assessment) 12.6 Late commissions 12.7 Unlicensed assessments 12.8 Getting a second opinion 12.9 Fault-finding APPENDIX A: PRF Summary Tables Broadleaved tree species Coniferous tree species APPENDIX B: PRF Recording Form References Bibliography Index This is a guide to finding tree-roosts for ecologists and tree-care professionals. It is the result of the collaborative efforts of surveyors and amateur naturalists across Europe as part of the Bat Tree Habitat Key project.