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Dynamics of a Problematic Vulture Roost in Southwest Florida and Responses of Vultures to Roost-Dispersal Management Efforts

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Dynamics of a Problematic Vulture Roost in Southwest Florida and Responses of Vultures to Roost-Dispersal Management Efforts DYNAMICS OF A PROBLEMATIC VULTURE ROOST IN SOUTHWEST FLORIDA AND RESPONSES OF VULTURES TO ROOST-DISPERSAL MANAGEMENT EFFORTS A thesis Presented to The Faculty of the College of Arts and Sciences Florida Gulf Coast University In Partial Fulfillment Of the Requirement for the Degree of Master of Science By Betsy A. Evans 2013 APPROVAL SHEET The thesis is submitted in partial fulfillment of the requirements for the degree of Master of Science __________________________________ Betsy A. Evans Approved: December 2013 __________________________________ Jerome A. Jackson, Ph.D. Committee Chair / Advisor __________________________________ Edwin M. Everham III, Ph.D. Committee Member __________________________________ Charles W. Gunnels IV, Ph.D. Committee Member The final copy of this thesis has been examined by the signatories, and we find that both the content and the form meet acceptable presentation standards of scholarly work in the above mentioned discipline. iii ACKNOWLEDGMENTS First and foremost I thank my thesis advisor, Dr. Jerry Jackson, whose support, assistance, and interest throughout the whole process was vital in the preparation and completion of this project. I am grateful to my committee members, Dr. Billy Gunnels and Dr. Win Everham, who provided statistical guidance and vital assistance in the interpretation and editing of the project. I am appreciative to the Department of Marine and Ecological Sciences and the Department of Biological Sciences at Florida Gulf Coast University for their support and encouragement during the completion of my degree. Additionally, I thank the Guadalupe Center of Immokalee for allowing me to conduct research on their property and providing valuable information during the project. A special thank you to the Ding Darling Wildlife Society for their generosity in providing supplemental funding for the project. I would like to thank my family and friends for their encouragement and positivity while I completed my thesis work. And last, but not least I would like to thank my husband, Lucas Halverson, whose assistance with data collection was invaluable and whose positivity gave me the strength to finish my graduate degree. iv ABSTRACT North American populations of Black Vultures (Coragyps atratus) and Turkey Vultures (Cathartes aura) are steadily increasing and their ranges are expanding, and both species are common in southwest Florida. Success of these species in the United States has led to a rise in conflicts between humans and vultures and an increased need for effective vulture management. The occurrence of a problematic vulture roost at the Guadalupe Center of Immokalee, an early childhood education center in southwest Florida, was the focal point for a conflict between humans and vultures. The Center had up to 250-300 vultures on their property on a daily basis throughout most of the year. Vultures were observed perching on the Center building and surrounding structures, as well as using an associated retention pond for bathing and drinking, and adjacent mowed areas for social interactions. The primary objective of this study was to evaluate and determine site-specific solutions to a vulture roost location problem. In order to provide site-specific solutions to vulture roost problems, an understanding of vulture behavior and roost habitats used by vultures was essential to determine why the Guadalupe Center and areas surrounding it were attractive as a roost site. A secondary objective included the evaluation of management techniques that were initiated by the Center and were not site-specific. The overall goal was to evaluate vulture management techniques available, to reduce and disperse the vultures on the property, and reduce vulture- caused damage. The Guadalupe Center roost was compared to 26 vulture roosts in the United States. Of the 15 roosts observed in Florida, all were associated closely with water suggesting an importance of water to vulture roost location. Air currents, such as obstruction currents were v present in over 70% of the roosts analyzed suggesting the importance of air current production to the proximity of roost sites. After the implementation of site-specific management techniques, the total population of vultures on the property decreased significantly. The total population of vultures did not decrease significantly after the initiation of non-site-specific management techniques. The areas of the property the vultures occupied differed between pre- and post- management. During roof-area management, vultures used the forested area north of the Center’s property more often than expected and used the fences, pond, and building less often than expected, suggesting that site-specific management efforts were effective at dispersing the birds and reducing their impact on the property. Non-site-specific Center-initiated management did not have a long-term effect on the population; birds readily habituated to the strategies (deployment of vulture carcasses and pinwheels) and were observed more often than expected on all areas of the Center’s property. The behavior of the birds at the Guadalupe Center did not differ significantly when comparing pre-management to any management strategy suggesting that management did not prevent vultures from engaging in behaviors essential for survival. Consistency and persistency are keys to effectively managing a problematic vulture roost. When the Center initiated non-site-specific management techniques, the vultures did not alter their use of the property. Since the management initiated by the Center was not consistent, vultures were able to readily habituate to the deterrents. Management of vultures should be a site-specific gradual process. Understanding behavior and roost habitat parameters is essential to developing effective management strategies for vultures. vi TABLE OF CONTENTS ACKNOWLEDGMENTS .............................................................................................. iii ABSTRACT .................................................................................................................. iv TABLE OF CONTENTS ............................................................................................... vi LIST OF FIGURES ..................................................................................................... viii LIST OF TABLES .......................................................................................................... x INTRODUCTION .......................................................................................................... 1 MATERIALS AND METHODS Study area ............................................................................................................ 5 Roost habitat characteristics............................................................................... 11 Pre-observational control data collection ........................................................... 12 Management techniques .................................................................................... 15 Post-management data collection ....................................................................... 23 Data analysis ..................................................................................................... 23 RESULTS Roost habitat characteristics............................................................................... 25 Guadalupe Center roost composition ................................................................. 28 Management techniques .................................................................................... 30 Behavior ............................................................................................................ 43 vii DISCUSSION Guadalupe Center vulture roost composition...................................................... 45 Vulture response to management efforts ............................................................ 45 Use of noise, visual, and chemical repellants in vulture management ................. 47 Role of roost habitat characteristics in vulture management ............................... 51 Importance of vulture behavior in management plans ........................................ 53 Community activities contributing to vulture roost problems ............................. 55 What made the Guadalupe Center attractive as a roost site? ............................... 57 Need for effective vulture management ............................................................. 59 APPENDIX A Black and Turkey vulture species information ................................................... 62 APPENDIX B Problems associated with vulture use of the Guadalupe Center property ............ 69 APPENDIX C Ineffectiveness and limitations in the implementation of the management techniques of the Guadalupe Center roost .......................................................... 78 APPENDIX D Future management suggestions for the Guadalupe Center roost site and other problematic vulture roosts.................................................................................. 83 LITERATURE CITED ................................................................................................. 87 viii LIST OF FIGURES Figure 1: Map of study area in Collier County, Florida .................................................... 6 Figure 2: Aerial photograph of Immokalee, Florida ........................................................ 8 Figure 3: Aerial photograph of the Guadalupe Center ...................................................
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