CONSEQUENCES OF WEED INVASION AND CONTROL ON PLANT-BIRD INTERACTIONS AND BIRD COMMUNITIES A thesis submitted in fulfilment of the requirements for the award of the degree Doctor of Philosophy from UNIVERSITY OF WOLLONGONG by Carl R. Gosper, B. Nat. Res. (Hons) DEPARTMENT OF BIOLOGICAL SCIENCES 2004 CERTIFICATION I, Carl R. Gosper, declare that this thesis, submitted in fulfilment of the requirements for the award of Doctor of Philosophy, in the Department of Biological Sciences, University of Wollongong, is wholly my own work unless otherwise referenced or acknowledged. The document has not been submitted for qualifications at any other academic institution. Carl R. Gosper 10 September 2004 C.R. Gosper Weed invasion and plant-bird interactions Table of Contents List of Figures...................................................................................................................... ix List of Tables ........................................................................................................................ x Abbreviations and conventions............................................................................................ xi Abstract.. ............................................................................................................................ xiii Acknowledgments............................................................................................................... xv CHAPTER 1. GENERAL INTRODUCTION...................................................................... 1 1.1 PLANT-ANIMAL INTERACTIONS..................................................................................... 3 1.2 INVASIVE SPECIES AND THEIR ECOLOGICAL IMPACTS .................................................. 3 1.2.1 Disruption of plant-animal interactions by biological invasions .......................... 4 1.2.2 Effects of invasive plants on plant-animal interactions and fauna communities .. 4 1.3 MANAGEMENT OF INVASIVE PLANTS AND ITS EFFECTS ON PLANT-ANIMAL INTERACTIONS AND FAUNA COMMUNITIES ................................................................. 6 1.4 INVASIVE PLANTS IN AUSTRALIA.................................................................................. 7 1.4.1 Interactions and effects of invasive plants on birds in Australia........................... 7 1.5 STUDY SPECIES – BITOU BUSH (CHRYSANTHEMOIDES MONILIFERA SPP. ROTUNDATA)..8 1.5.1 Invasive C. monilifera in Australia ....................................................................... 8 1.5.2 Ecology of C. monilifera..................................................................................... 10 1.5.3 Effects of C. monilifera invasion on biodiversity ............................................... 11 1.5.4 Control of C. monilifera...................................................................................... 11 1.6 THIS STUDY ................................................................................................................. 12 1.6.1 Thesis outline ...................................................................................................... 14 CHAPTER 2. FRUIT CHARACTERISTICS OF CHRYSANTHEMOIDES MONILIFERA AND A COMPARISON WITH CO-OCCURRING NATIVE PLANT SPECIES…….......................................................................................................................15 2.1 INTRODUCTION............................................................................................................ 17 2.2 METHODS .................................................................................................................... 17 2.3 RESULTS...................................................................................................................... 19 2.3.1 Morphology......................................................................................................... 19 2.3.2 Nutrient content................................................................................................... 19 2.3.3 Periods of inflorescence and fruit production ..................................................... 21 2.4 DISCUSSION................................................................................................................. 22 2.4.1 Morphology......................................................................................................... 22 2.4.2 Nutrient content................................................................................................... 24 v C.R. Gosper Weed invasion and plant-bird interactions 2.4.3 Periods of inflorescence and fruit production ..................................................... 24 2.4.4 Conclusion .......................................................................................................... 26 CHAPTER 3. PLANT FOODS OF BIRDS IN COASTAL NSW AND PREDICTED IMPACTS OF CHRYSANTHEMOIDES MONILIFERA ON PLANT-BIRD INTERACTIONS ................................................................................................................ 29 3.1 INTRODUCTION............................................................................................................ 31 3.2 METHODS .................................................................................................................... 32 3.3 RESULTS...................................................................................................................... 33 3.3.1 Plant visitors........................................................................................................ 33 3.3.2 Bird diets............................................................................................................. 34 3.3.3 Temporal patterns of plant resource availability................................................. 35 3.4 DISCUSSION................................................................................................................. 36 3.4.1 Study biases ........................................................................................................ 36 3.4.2 Plant-bird interactions......................................................................................... 37 3.4.3 Predicted effects of C. monilifera invasion and control...................................... 42 3.4.4 Conclusion .......................................................................................................... 45 CHAPTER 4. INVASIVE BITOU BUSH (CHRYSANTHEMOIDES MONILIFERA SSP. ROTUNDATA) FRUITS AS FOOD FOR BIRDS IN EASTERN AUSTRALIA ........... 61 4.1 INTRODUCTION............................................................................................................ 63 4.2 METHODS .................................................................................................................... 64 4.3 RESULTS...................................................................................................................... 64 4.3.1 Dispersers............................................................................................................ 65 4.3.2 Predators ............................................................................................................. 67 4.3.3 Pulp consumers ................................................................................................... 67 4.4 DISCUSSION................................................................................................................. 67 4.4.1 Bird species that use C. monilifera fruits............................................................ 67 4.4.2 Fruit and crop characteristics of C. monilifera.................................................... 69 4.4.3 Conclusion .......................................................................................................... 69 CHAPTER 5. THE EFFECT OF CHRYSANTHEMOIDES MONILIFERA MANAGEMENT ON THE RATE OF REMOVAL OF VERTEBRATE-DISPERSED FRUITS…… ......................................................................................................................... 71 5.1 INTRODUCTION............................................................................................................ 73 5.2 METHODS .................................................................................................................... 75 5.2.1 Study areas.......................................................................................................... 75 5.2.2 Study species....................................................................................................... 76 vi C.R. Gosper Weed invasion and plant-bird interactions 5.2.3 Experimental stations.......................................................................................... 77 5.2.4 Experimental design............................................................................................ 78 5.2.5 Statistical analysis............................................................................................... 79 5.3 RESULTS...................................................................................................................... 80 5.4 DISCUSSION................................................................................................................. 85 5.4.1 Effects of habitat ................................................................................................. 85 5.4.2 Effects of location ............................................................................................... 88 5.4.3 Differences in removal rates between species ...................................................