The urban Herring gull, foraging niche and interactions with humans Submitted by Luke Edwyn Marsh to the University of Exeter as a thesis for the degree of Masters by Research in Biological Sciences, 14th April, 2020 This thesis is available for Library use on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement. I certify that all material in this thesis which is not my own work has been identified and that any material that has previously been submitted and approved for the award of a degree by this or any other University has been acknowledged. (Signature) ……………………………………………………………………………… 1 ABSTRACT Gulls (Laridae) are of significant interest because of their use and breeding in urban environments, which has increased human-wildlife conflicts. However, there is a lack of information that summarises population trends in gulls, that is driving them towards conflicts with humans; the attitude towards gulls that the public has, especially in urban environments and the factors that determine those attitudes; and how gulls utilise the urban environment for reproductive success. In this thesis, I explore the literature around gull trends throughout the Western Hemisphere. Using a questionnaire, I attempt to collate information about the public’s attitude towards gulls, paired with spatial correlation to demonstrate geographic differences. I also use gull pellets and foraging effort to explore the niche of gulls, and test for differences between urban and rural birds. The findings show gull population changes are constant, and that public attitude is negative towards gulls, with age and knowledge about gulls effecting negative perceptions. I also demonstrate that rural and urban gulls have differing habitat use periodically through the breeding season but have commonality in foraging effort. 2 CONTENT ABSTRACT .................................................................................................... 2 CONTENT ....................................................................................................... 3 LIST OF FIGURES, TABLES & EQUATIONS ............................................... 5 Tables .......................................................................................................... 5 Figures ......................................................................................................... 6 MAIN SUMMARY ........................................................................................... 9 CHAPTER 1: POPULATION CHANGES OF NORTH-WESTERN HEMISPHERE GULLS INTO THE 21th CENTURY ...................................... 12 1.1. INTRODUCTION .................................................................................... 12 1.2. NORTH AMERICA ................................................................................. 14 1.2.1. American herring gull ....................................................................... 14 1.2.2 Laughing gull .................................................................................... 15 1.2.3. Black-legged kittiwake ..................................................................... 16 1.2.4. Ivory gull .......................................................................................... 17 1.2.5. Glaucous-winged gull ....................................................................... 18 1.2.6. Great black-backed gull ................................................................... 19 1.2.7. Glaucous gull ................................................................................... 20 1.3. MAINLAND EUROPE AND THE NORTHERN ATLANTIC ................... 22 1.3.1. Audouin's gull ................................................................................... 22 1.3.2. European herring gull ....................................................................... 23 1.3.3. Lesser black-backed gull ................................................................. 24 1.3.4. Yellow-legged gull ............................................................................ 25 1.3.5. Slender-billed gull ............................................................................ 27 1.3.6. Mediterranean gull ........................................................................... 28 1.4. THE BRITISH ISLES & IRELAND ......................................................... 30 1.4.1. Great black-backed gull (UK & Ire.) ................................................. 30 1.4.2. European herring gull (UK & Ire.) ..................................................... 32 1.4.3. Black-legged kittiwake (UK & Ire.).................................................... 34 1.5. REVIEW OF TABLE DATA ................................................................... 36 1.6. DRIVERS OF POPULATION TRENDS ................................................. 37 1.6.1. Scavenging behaviour and adaptation to human landscapes .......... 37 1.6.2. Climate and environmental quality ................................................... 39 1.6.3. Influence on other species ............................................................... 40 1.6.4. Inter-colony movements ................................................................... 41 1.7. EFFECTS OF POPULATION CHANGE & CONFLICTS ....................... 42 1.7.1. Predation on other seabirds ............................................................. 42 1.7.2. Cannibalism ..................................................................................... 43 1.7.3. Human-gull conflicts ......................................................................... 43 3 1.8. MITIGATION & CONSERVATION PRIORTIES .................................... 45 1.8.1. Identification of trends ...................................................................... 45 1.8.2. Goals for future conservation ........................................................... 47 1.9. CONCLUSIONS ..................................................................................... 51 CHAPTER 2: WILDLIFE CONFLICTS: URBAN GULLS, WHAT THE PUBLIC THINKS ............................................................................................................ 52 2.1. ABSTRACT ........................................................................................... 52 2.2. INTRODUCTION .................................................................................... 53 2.2.1. Human–Wildlife Conflict ................................................................... 53 2.2.2. Urban gulls, the problem .................................................................. 54 2.2.3. Study Aims ....................................................................................... 58 2.3. METHOD................................................................................................ 59 2.3.1. Measuring public perception of gulls ................................................ 59 2.3.2. Survey design and administration .................................................... 61 2.2.3. Data Analysis ................................................................................... 63 2.4. RESULTS .............................................................................................. 66 2.4.1. Likert results measuring attitude ...................................................... 66 2.4.2. Demographic effects to attitude ....................................................... 69 2.4.3. Spatial Willingness to Pay affects to attitude.................................... 71 2.4.4. Economic effects to attitude ............................................................. 73 2.5. DISCUSSION ......................................................................................... 75 CHAPTER 3: NICHE OVERLAP AND FORAGING BUDGETS ...................... 79 3.1. ABSTRACT ........................................................................................... 79 3.2. INTRODUCTION .................................................................................... 80 3.2.1. The foraging niche of gulls ............................................................... 81 3.2.2. Study aims ....................................................................................... 85 3.3. METHOD................................................................................................ 86 3.3.1. Study Sites and Experimental Design .............................................. 86 3.3.2. Statistical Analysis ........................................................................... 88 3.4. RESULTS .............................................................................................. 91 3.4.1. Dietary profile of gulls ...................................................................... 91 3.4.2. Niche measurement ......................................................................... 97 3.4.3. Foraging effort................................................................................ 102 3.5. DISCUSSION ....................................................................................... 104 CHAPTER 4: CONCLUSIONS & FUTURE RESEARCH .............................. 109 4.1. Main Findings.................................................................................... 109 4.2. Further Study and Focus .................................................................. 110 APPENDIX .................................................................................................. 176 4 LIST OF FIGURES, TABLES & EQUATIONS Tables Table 1. Literature indicating