I POPULATION SIZE of BLUE-FOOTED BOOBIES IN
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POPULATION SIZE OF BLUE-FOOTED BOOBIES IN GALÁPAGOS: EVALUATION OF INDICATIONS OF POPULATION DECLINE BY DAVID ANCHUNDIA A Thesis Submitted to the Graduate Faculty of WAKE FOREST UNIVERSITY GRADUATE SCHOOL OF ARTS AND SCIENCES in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Biology May 2013 Winston-Salem, North Carolina Approved By: David J. Anderson, Ph.D., Advisor Miles R. Silman, Ph.D., Chair Todd M. Anderson, Ph.D. i DEDICATION This work is dedicated to the memory of my loving mother Juana Isabel Gonzalez. I thank her for all the support and the encouragement she gave me to study sciences. Also I thank my father Oswaldo Anchundia for his constant support during all this time. I will always appreciate all that they have done for me; this degree is dedicated to them. David J. Anchundia Gonzalez ii ACKNOWLEDGEMENT I want to express my sincere gratitude to my advisor Prof. David John Anderson for all the advice, motivation, enthusiasm, and immense knowledge that he shared with me during my M. S. study and research. Also I thank my lab mates Jacquelyn Grace, Felipe Estela, Emily Tompkins, and Terri Mannes for the help and guidance in my research. I want to thank the Prof. Miles Silman and Prof. Michael Anderson, who were part of my thesis committee, and the Professors of the Biology Department from Wake Forest University who shared their knowledge with me. I would like to express my gratitude to: Prof. Kathryn Huyvaert from Colorado State University, who helped me in parts of the analysis and modeling parts of the project; Kyle Anderson from Idaho State University, who helped with part of the GIS analysis; Professors Peter and Rosemary Grant from Princeton University, who provided unpublished breeding and attendance data from Daphne Island; and Lisa Balance and Robert Pitman from the National Marine Fisheries Service (La Jolla) for sharing unpublished at-sea distribution data. I thank all the field assistants that helped me in the collection of the data, and also staff scientists and collaborators of Charles Darwin Research Station who helped me in the collection of the data for the population estimate. I want to thank the Galápagos Conservancy and Galápagos Conservation Trust for the funding support of the project. Finally I want to thank Wake Forest University and the Biology Department for giving me the opportunity to be part of this prestigious University. iii TABLE OF CONTENTS List of Tables ..................................................................................................................... vi List of Figures ................................................................................................................... vii Abstract ............................................................................................................................ viii Introduction ........................................................................................................................ ix CHAPTER 1. Population size of blue-footed boobies in Galápagos: evaluation of indications of population decline ........................................................................................1 Abstract ............................................................................................................................1 Introduction ......................................................................................................................2 Methods ............................................................................................................................5 Results ............................................................................................................................13 Discussion ......................................................................................................................19 Tables ..............................................................................................................................26 Figures............................................................................................................................33 Literature Cited .............................................................................................................39 APPENDIX 1 .................................................................................................................43 APPENDIX 2 .................................................................................................................53 APPENDIX 3 .................................................................................................................59 CHAPTER 2. Implications of movement over the Perry Isthmus, Galápagos for seabird biogeography......................................................................................................................62 Abstract ..........................................................................................................................62 iv Introduction ....................................................................................................................62 Methods ..........................................................................................................................63 Results ............................................................................................................................64 Discussion ......................................................................................................................65 Tables ..............................................................................................................................68 Figures............................................................................................................................69 Literature Cited ..............................................................................................................70 Curriculum Vitae ...............................................................................................................71 v LIST OF TABLES CHAPTER 1. Table 1. Schedule of visits and activities done at each colony .....................................26 Table 2. Number of blue-footed boobies counted during coastline surveys in 2011 (single observer, over 11 weeks) and 2012 (double observer, five teams, over three consecutive days) ...........................................................................................................27 Table 3. Breeding activity at colonies in 2011 and 2012 in relation to historical maxima ...........................................................................................................................28 Table 4. Representation of prey items by weight in regurgitation samples ..................29 Table 5. Log likelihood, AIC, and derivative values for models explaining variation in breeding POTENTIAL (see Methods) ...........................................................................31 Table 6. β values and their standard errors for predictors in the model set of ..............32 CHAPTER 2. Table 1. Schedule of visits and activities done at each colony .....................................68 vi LIST OF FIGURES CHAPTER 1. Figure 1. Location of focal and non-focal colonies, islands, and section scanned per day during coastal survey of June 2012 .........................................................................33 Figure 2. Proportion of total grams of each fish in regurgitation samples ....................34 Figure 3. Proportion of total number of fish items collected in regurgitations samples 35 Figure 4. Foraging sites of adults blue-footed boobies, identified from kernel analysis of tracks from GPS tags .................................................................................................36 Figure 5. Duration and number of trips for tagged individuals ....................................37 Figure 6. Distribution of juvenile blue-footed boobies in the Eastern Tropical Pacific from ship-based survey, 1988-2006 ...............................................................................38 CHAPTER 2. Figure 1. Isabela Island and location of the Isthmus Perry ...........................................69 vii ABSTRACT Census and survey data for blue-footed boobies (Sula nebouxii excisa) in Galápagos, Ecuador from 2011-2012 indicated a population reduction, probably by more than 50%. Anthropogenic effects such as introduced predators are unlikely to explain this decline, because islands with and without such factors exhibited the same low breeding. The poor reproduction seems to be linked to scarcity of food. Previous studies indicated that sardine and herring (Clupeidae) support successful breeding, but these fish were mostly absent from the diet. Elsewhere in the eastern Pacific, sardines have decreased dramatically in abundance by natural processes in the last 15 years, as part of a well-documented and apparently natural cycle. This cyclic change in abundance provides an explanation for the recent demographic changes in blue-footed boobies in Galápagos. Land barriers have been mentioned as one of the mechanisms that promote population differentiation in pelagic seabirds, at what scale does a land barrier restrict gene flow effectively? Genetic data indicate that the Isthmus of Panamá does restrict gene flow in boobies and other seabirds. I evaluated a smaller isthmus (the Perry Isthmus) that could allow transit across Isabela Island, Galápagos. Daytime observations revealed crossings by > 48 blue-footed boobies and > 2 frigatebirds