Towards a Conservation Strategy of the Roseate Tern Sterna dougallii in the Azores Archipelago by Verónica Neves Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the University of Glasgow, Division of Environmental and Evolutionary Biology, November 2005 © Verónica C. Neves 2005 Candidates Declaration I declare that the work described in this thesis has been carried out by myself unless otherwise cited or acknowledged. Part of the material included in this thesis is being prepared for submission and part has been submitted and published in co-authorship with others: Chapter 5. Published as: Neves V. C., Murdoch N. & Furness R. W. Population Status and Diet of Yellow-Legged Gull in the Azores. Arquipelago, Life and Marine Sciences (in press). Arquipelago, Life and Marine Sciences. Chapter 6. Published as: Neves V. C., Panagiatakopoulos S. & Furness R. W. A control taste aversion experiment on predators of the Roseate Tern. European Journal of Wildlife research (in press). European Journal of Wildlife Research. Chapter 7. Submitted as: Bried J., Magalhães M., Bolton M., Neves V. C., Bell E., Pereira J. C., Aguiar L., Monteiro L. R. & Santos R. S. Seabird habitat restoration on Praia islet, Graciosa (Azores): a success story. Appendix 3. León A, Mingués E, & Neves, V. C. 2005. Factors affecting breeding distribution and seabird richness within the Azores archipelago. Seabirds, 7: 15-22. Appendix 5. Hays H., Neves V. C. & Lima P. 2002. Banded Roseate Terns from different continents trapped in the Azores. Journal of Field Ornithology, 73: 180-184. Appendix 6. Neves V. C., Bremer E. & Hays H. 2002. Recovery in Punta Rasa, Argentina of Common Terns banded in the Azores Archipelago, North Atlantic. Waterbirds, 25: 459-461. I further declare this thesis is entirely of my own composition and has not, in whole or in part, been submitted for any other degree. Verónica Neves November 2005 ii Dedicated to the memory of Luís R. Monteiro (1962-1999) iii ABSTRACT The Roseate Tern, Sterna dougallii, is currently regarded as one of the most endangered seabirds in Europe. The mid-Atlantic Azores islands, Portugal, are an important breeding ground for this species, holding more than 50% of the European population. EU directives are aimed at maintaining and enhancing the current range and breeding numbers of Roseate Tern in the Azores and elsewhere and it is thus a priority species on the Conservation Agenda. However, few studies have examined the Roseate Tern in this geographical area of the Atlantic, and this thesis aims to address this need. The thesis investigates and examines several potential factors affecting breeding numbers of these birds in the archipelago, giving particular attention to predation and potential predators. Data were mainly obtained through fieldwork conducted in the period 2002-2004, but investigation of recent historical records of breeding numbers is utilized to assess trends. These historical data were collected between 1989 and 2005, and show that the breeding population has fluctuated widely over the last 16 years. Taking the Roseate Tern demographic parameters into account, this variation can only be explained by means of intermittent breeding. Many more years of research and monitoring will be needed before we can fully understand the factors underlying the decision of Roseate Terns to breed or not in a given year in the archipelago. Nevertheless this lack of a complete understanding of a perhaps natural variation does not prevent implementation of immediate conservation action. This thesis examines the impact of avian predators, such as gulls and starlings, on breeding success. Although terns and starlings can nest in close proximity in the Azores, egg predation by starlings has rarely been reported. In the Azores, this behaviour has only been detected in one colony, Vila islet that holds about 20% of the Azorean Roseate Tern population, but it is the main cause of egg losses in the tern colony. A census conducted to estimate the size of the Yellow-legged Gull population yielded an estimate of 4249 breeding pairs, representing an increase of almost 60% from the previous survey conducted in 1984. A control taste aversion (CTA) experiment was conducted to explore the possibility of using this technique as a way to reduce starling and gull predation. Our results indicate that CTA has potential to work with gulls but it will be much more difficult to use it successfully on starlings. Using an integrated habitat management strategy at Praia Islet, Graciosa, I demonstrate that it is possible to enhance the habitat of the terns and increase their breeding numbers if efforts are global and broad. Future conservation action might need to implement lethal control of starlings in very specific situations. Lethal control should only be undertaken in conjunction with other measures, such as provision of Roseate Tern artificial nests and close monitoring to assess its effect on productivity. The thesis concludes by summarizing the management and conservation implications of the results and placing these ornithological findings in a wider conservation perspective. By rapidly implementing the actions here described, the populations of Roseate Terns should increase in future to the point where it is no longer critically endangered. iv Acknowledgments First of all I would like to thank Bob Furness for his challenging and very rewarding supervision through the various courses of this thesis. He has never failed to come back to me incredibly fast with comments and suggestions to the drafts I was extremely slow giving him in the first place. Additionally, he has given great assistance with the organization of the Azores 2003 Expedition. Andrew Thompson and Elsa João have generously commented, given good ideas and proofread and I am very grateful for their help and feedback. Their enthusiasm and willingness to help have inspired me ever since I’ve met them. Comments by Jöel Bried, Jacob González-Solís and other anonymous reviewers, as well as editors, also helped to improve some chapters. I am grateful to the Portuguese Foundation for Science and Technology (FCT-MCTES) for funding my four years of study at Glasgow University (grant reference SFRH/BD/3436/2000). I also want to thank the Carnegie Trust for the Universities of Scotland, the Royal Geographical Society, the Seabird Group, the Glasgow Natural History Society, the Glasgow University Court, Câmara Municipal de Santa Cruz da Graciosa and SATA Air Azores for funding the Azores 2003 Expedition. The Azores Environmental Council (Secretaria Regional do Ambiente e do Mar), and the Seabird Group helped financing the 2004 Gull Census. The EU Exchange Programme Eurodyssee, coordinated in the Azores by Mr. José Carvalho, supported my field assistants in 2002 and 2003, Inga Diasamidze and Juan Simón. Ricardo S. Santos (University of the Azores) kindly made available the equipment, laboratories and collections at the Dept. of Oceanography & Fisheries (DOP). Additionally he also granted me access to the data used on chapters II. A great number of researchers, technicians and volunteers collected the data through the years, under the late Luís Monteiro coordination, and I would specially like to thank (in chronological order): J. Ramos, J. Pereira, R. Feio, M. Gróz, L. Aguiar, A. Silva, A. Mendes, M. Cormons, M. Carvalho, M. Bolton and J. Bried. M. Carvalho, J. Bried and F. Cardigos, all from DOP, gave logistic support at different stages of the fieldwork. I am very grateful to Anaíd Diaz for help and suggestions on chapter II. Norman Ratcliffe at RSPB gave helpful suggestions and comments on Chapter III and kindly produced the renesting model used and suggested the idea in the first place. Ricardo Medeiros kindly produced the maps for Chapter II and Sónia Mendes for chapter V. Paul Johnson and Eric Pasquet gave advice on the early stages of choosing a molecular technique to study genetic diversity of starlings. Kate Orr introduced me to the mtDNA laboratory techniques and procedures with extreme v clarity and patience at a time when I was struggling to make progress with my work. Her constant good humour and availability to help have also been much appreciated. Barbara Mable has given crucial and extensive help with the data analysis in chapter IV; without her I would probably still be struggling with MacClade and Harlequin. She was also fundamental on the choice of gene and primers used to sequence it and I am thankful for all her help. Jane Reid kindly allowed me to use her blood samples from Fair Isle and Oriol Clarabuch & Jacob González-Solís generously collected the Spanish samples. An anonymous collector provided the Bristol samples. Roger Downie suggested organizing an expedition to the Azores, under the auspices of the Glasgow University Exploration Society, and I thank him for the idea and initial support. Dirk Nolf from the Belgian Royal Museum of Natural History welcomed me at his house in Bruges to use his fantastic otoliths collection. I would have been completely lost amongst specimens from more than 6000 fish species but he generously gave me his time to assist with the identification. I don’t think I could have come across a better person to help me with this task. Without him the percentage of unidentified otoliths in gull diets would undoubtfully be much, much higher. To start with, he actually did most of the identification but I gradually grew otoliths-identification-addicted. Additionally Dirk and his wife Dora were fantastic hosts; their sense of humour, fabulous cooking skills and extraordinary wine taste made for a great time, but it was their generosity, support and encouragement that touched me the most. Matt Cormons has also given support and innumerable useful suggestions and I thank him for believing in me even when I didn’t. For help with fieldwork I am grateful to (chronological order again): Inga Diasamidze, Luís Aguiar, Pedro Domingos, Paulo Faria, Jorge Caetano, Sotirios Panagiotakoupolos, Juan Simón, Márcia Santos, Henrique Simões, Hélder Fraga, Matt Cormons, Nadia Murdoch, Luís Filipe, João Monteiro, José Matos and the members of the Azores 2003 Expedition.