POPULATION VIABILITY AND CONSERVATION OF GREY PARROTS PSITTACUS ERITHACUS ON THE ISLAND OF PRÍNCIPE, GULF OF GUINEA S VALLE PhD 2015 POPULATION VIABILITY AND CONSERVATION OF GREY PARROTS PSITTACUS ERITHACUS ON THE ISLAND OF PRÍNCIPE, GULF OF GUINEA SIMON VALLE A thesis submitted in partial fulfilment of the requirements of the Manchester Metropolitan University for the degree of Doctor of Philosophy School of Science and the Environment the Manchester Metropolitan University 2015 Abstract Parrots are among the most endangered birds in the world, owing to the international pet trade, and habitat degradation. Grey Parrot Psittacus erithacus, the most traded wild-caught species, has suffered a steep decline across its vast African range. This PhD investigates Grey Parrot’s ecology to understand the mechanisms by which harvest and habitat loss affect populations. The island of Príncipe was chosen as a study area owing to its healthy Grey Parrot population, its tradition of parrot harvest and the disturbed-to-pristine range of habitats. Parrot densities were exceptionally high (mean±SE: 53±3 parrots km-1), and their distribution within the island was shown to change significantly between pre- and post-breeding season. The presence of nest tree species was the best predictor of densities in the former (F=2.99, p=0.07), while slope and food tree species were in the latter (F=3.0, p<0.05 and F=8.04, p<0.01). Variation in habitat use across seasons highlights the importance of opportunely timed surveys, and the need of preserving a matrix of habitats. Three simple and inexpensive methods were tested, which may be useful where more precise methods cannot be used. Simple encounter rates were shown to be a workable proxy for actual densities: a relationship was found between the two (R2=0.8, df=9, p=0.01). Long watches proved to be far less accurate and suitable only in limited cases (i.e. enough vantage points overlooking small areas and numerous encounters). Counts along flyways were suggested to be a good monitoring method, although further testing is required. Nest densities were found to be very high (mean±SE: 16.8±7.9 and 72.4±26.2 nests km-2 in secondary and primary forest respectively) compared to those elsewhere. The habitat characteristics measured didn’t affect productivity, suggesting that cavity characteristics may be more important. The best demographic data available on the species, were used to build a Population Viability Model to investigate its population dynamics in the face of harvest and habitat loss. In Príncipe, Grey Parrots were shown to have increased rapidly after a trade ban was put in place, highlighting the recovery potential of the species. Harvest alone was shown to be harmless only when small quotas (e.g. 600 chicks year-1) are yielded from large populations, while habitat loss lowered the predicted maximum population size. The interaction of these threats can be much more unpredictable. The effects of harvest are worsened if poorly regulated or techniques that include the harvesting of adults are used. Extinctions were predicted to occur with significant delay (≥40 years), and the conservation implications were discussed. Finally, the contribution of this thesis to the understanding of Grey Parrots ecology and conservation is highlighted and research priorities identified. Acknowledgements First and foremost, I am eternally grateful to my parents who supported and encouraged me to follow my dreams ever since I started collecting bugs as a child, no matter how far this took me from home. Grazie. I indebted to Prof Stuart Marsden for patiently guiding me throughout my PhD, with his unconventional wittiness (and jokes), offering me continuous opportunities to improve my skills and experience. I am greatly thankful to Prof Nigel Collar for being incredibly supportive all along, with swift and valuable feedback on any manuscript no matter how busy his schedule. Thank you also to Dr Ed Harris and Dr Martim Melo for their input sharing their knowledge on statistical methods and ornithology in the Gulf of Guinea, respectively. This research would not have been possible without the financial support of Parrots International. I’d explicitly like to thank Dr Mark Stafford, the director and president, and the generous members who donated towards this project. The work on the island of Príncipe was facilitated by Eng. Arlindo Carvalho, National General Director of the Environment, Eng. Nestor Umbelina, regional Secretary to the Infrastructures and the Environment, and Daniel Ramos, director of the Parque Natural d’ Ôbo do Príncipe. None of the fieldwork would have been possible without the guiding skills of Satiro. HBD kindly provided logistical support during all the fieldwork on Príncipe. Thank you also Lynsey Crellin and Filippo Marolla for their help in the collection of part of the data. I am grateful to Rita Alves, Ana Cabral and her family, Sergio Campos, Joana Hancock, Madalena Patacho and Anibal Serra for their friendship in the long months in Príncipe. Finally I am profoundly indebted to Nikki Wolf who over three and a half years has looked after me with loving care, in times of both enthusiasm and discouragement, always managing to make me smile. i ii Table of Contents Population viability and conservation of Grey Parrots Psittacus erithacus on the island of Príncipe, Gulf of Guinea ........................................................................ i Abstract ............................................................................................................... v Acknowledgements .............................................................................................. i Chapter 1. Population Viability and the Conservation of Parrots: an introduction ............................................................................................................................ 1 1.1. The parrot conservation crisis ................................................................ 1 1.1.1. Habitat loss and fragmentation ........................................................ 3 1.1.2. International pet trade ..................................................................... 5 1.1.3. Other threats ................................................................................... 6 1.2. Parrot populations: density, demography and dynamics........................ 7 1.2.1. Estimating parrot abundance .......................................................... 7 1.2.2. Demography and population dynamics ........................................... 9 1.3. Population Viability Analysis as a tool for parrot conservation and management ................................................................................................. 10 1.4. The Grey Parrot in Príncipe: a case study ........................................... 12 1.5. Study species: the Grey Parrot ............................................................ 13 1.5.1. Taxonomy ..................................................................................... 13 1.5.2. Distribution .................................................................................... 14 1.5.3. Status and population trends ......................................................... 16 1.5.4. Habitat and ecology ....................................................................... 17 1.5.5. Threats and conservation .............................................................. 18 iii 1.6. Study site: The island of Príncipe ....................................................... 20 1.6.1. Geology and geomorphology ........................................................ 20 1.6.2. Climate .......................................................................................... 22 1.6.3. Vegetation ..................................................................................... 22 1.6.4. Biodiversity in the Gulf of Guinea .................................................. 23 1.6.5. Avian endemism ............................................................................ 24 1.7. Overall aim of the PhD and overview of the chapters .......................... 26 1.8. References .......................................................................................... 28 Chapter 2. Seasonality in habitat use by the superabundant Grey Parrot Psittacus erithacus on Príncipe, Gulf of Guinea ................................................ 47 2.1 Summary ............................................................................................. 47 2.2 Introduction .......................................................................................... 48 2.3 Methods ............................................................................................... 50 2.3.1 Study area and species ................................................................. 50 2.3.2 Population and density estimates .................................................. 51 2.3.3 Habitat characterization ................................................................ 53 2.3.4 Seasonality in parrot-habitat associations ..................................... 53 2.4 Results ................................................................................................. 54 2.4.1 Population size and density estimate ............................................ 54 2.4.2 Seasonality of parrot-habitat associations ..................................... 57 2.5 Discussion ........................................................................................... 61 2.6 References .........................................................................................