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TABLE OF CONTENTS ACKNOWLEDGEMENTS ................................................................................................................................ 4 RÉSUMÉ EN FRANÇAIS .................................................................................................................................. 6 ENGLISH SUMMARY ....................................................................................................................................... 7 CHAPTER 1 1.1 GENERAL INTRODUCTION .......................................................................................................................................... 8 1.2 GENERAL METHODS ................................................................................................................................................. 23 CHAPTER 2 ANALYSIS OF PLAYBACK CENSUS TO ESTIMATE THE DENSITY OF CAVITY-DWELLING BIRDS ............................................................................................................................................................... 28 2.1 INTRODUCTION ......................................................................................................................................................... 30 2.2 MATERIALS AND METHODS .................................................................................................................................... 32 2.3 RESULTS ..................................................................................................................................................................... 35 2.4 DISCUSSION ................................................................................................................................................................ 36 TABLES ............................................................................................................................................................................... 38 FIGURES ............................................................................................................................................................................. 39 EXTERNAL SUPPLEMENTARY MATERIALS (ESMS) .................................................................................................. 41 CHAPTER 3 ASSESSING POPULATION SIZE IN NOCTURNAL DWELLING SEABIRDS ACCOUNTING FOR DETECTION PROBABILITY AND HABITAT PREFERENCES: A SEQUENTIAL APPROACH ....... 42 3.1 INTRODUCTION ......................................................................................................................................................... 44 3.2 MATERIAL AND METHODS ....................................................................................................................................... 45 3.3 RESULTS ..................................................................................................................................................................... 49 3.4 DISCUSSION ................................................................................................................................................................ 51 TABLES ............................................................................................................................................................................... 55 APPENDIXES ...................................................................................................................................................................... 61 CHAPTER 4 COMPARATIVE FORAGING DISTRIBUTION AND ECOLOGY SUGGESTS INTERSPECIFIC COMPETITION BETWEEN TWO SYMPATRIC SHEARWATERS FROM THE SEYCHELLES ....... 72 4.1 INTRODUCTION ......................................................................................................................................................... 73 4.2 MATERIALS AND METHODS ..................................................................................................................................... 74 4.3 RESULTS ..................................................................................................................................................................... 78 4.4 DISCUSSION ................................................................................................................................................................ 81 TABLES ............................................................................................................................................................................... 84 FIGURES ............................................................................................................................................................................. 87 EXTERNAL SUPPLEMENTARY MATERIALS (ESMS) .................................................................................................. 92 CHAPTER 5 MOVEMENT PATTERNS AND HABITAT SELECTION OF WEDGE-TAILED SHEARWATERS (PUFFINUS PACIFICUS) BREEDING AT ARIDE ISLAND, SEYCHELLES ........................................... 96 5.1 INTRODUCTION ......................................................................................................................................................... 98 5.2 MATERIALS AND METHODS .................................................................................................................................... 98 2 5.3 RESULTS ................................................................................................................................................................... 100 5.4 DISCUSSION .............................................................................................................................................................. 101 TABLES ............................................................................................................................................................................. 103 FIGURES ........................................................................................................................................................................... 104 CHAPTER 6 GENERAL DISCUSSION ............................................................................................................................. 105 APPENDIX I BREEDING SUCCESS ANALYSIS OF TROPICAL SHEARWATER AND WEDGE-TAILED SHEARWATER POPULATIONS ON ARIDE ISLAND. ......................................................................... 113 BIBLIOGRAPHY .......................................................................................................................................... 115 3 Acknowledgements During this long and winding path I met many people and organizations that I would like to thank, whether for their physical, psychological, financial or scientific help. I start from the Seychelles, where it all begun. I would like to thank all the volunteers and staff members that contributed, even if with only a few hours, to the nocturnal and diurnal field work during the Shearwater’s project. In particular: Gwen Maggs, Melinda Curran and Roland Duval (Assistant Conservation Officers), Alex Underwood and Uzice Samedi (Island Managers), Juan Michel, Clifford Bresson, Anselm Barra, Jim Uzice, Shannon Adeline, Rodney Maria, Elvis Bristol (Conservation Rangers), Ian Bullok, Gill Lewis, Adam Moolna, Elizabeth Atchoi, Joao Lagoa, Sabine Laukamm, Agnes Wagner, Andrew Murray, Rebecca Melville, Daniel Turner, Sieglinde Fink, Heike Szmutka, Kat Machine, Rachel Kwok, Darrah Murphy, Romain All, Victor B., Lisa Fontanesi, Yuri Bukur (Volunteers), Javier Cotin, Susan Ansel and Russel Thompson (collaborators and friends). All these people did not only contributed to the field work but also gave me the opportunity to exchange differnt cultural points of view and to discover the world even saying sitll in a tiny island in the Indian Ocean. In a small community we shared everything, joy, pain, work, but especially love for nature and the willingness to do something for conservation. I really appreciated your help guys, but also the barbeques, the fishing trips, the gardening and the life together, that, even if very hard sometimes, was worth experiencing. Seychelles is also the base of the Island Conservation Society, the NGO that employed me for 5 years and that allowed me to complete my PhD in France. I would like to thank all its members in particular James Cadbury (Chairman ICS UK), Adrian Skerrett (Chairman), Alice Mascarenhas, Ahab Downer, Adam Moolna (CEOs), Pierre André Adam (Projects & Science Manager) and Dixon Bastienne (Finance & Administration Manager) from