Status and Use of Tropical Hardwood Hammocks and Forested Residential Areas As Habitat for Resident and Neotropical Migratory Birds in the Florida Keys
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STATUS AND USE OF TROPICAL HARDWOOD HAMMOCKS AND FORESTED RESIDENTIAL AREAS AS HABITAT FOR RESIDENT AND NEOTROPICAL MIGRATORY BIRDS IN THE FLORIDA KEYS By ANNISA KARIM A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2007 1 © 2007Annisa Karim 2 “In Wildness is the Preservation of the World.” -Thoreau/ Porter/ Metallica 3 ACKNOWLEDGMENTS I would like to express my enormous gratitude to my parents, Muneer and Laila, and to my sister, Farah, for their love and encouragement throughout my life. The advice and insight they have provided and their belief in me has enabled me to achieve my goals and follow my dreams. I am extremely fortunate to have them in my life! SHRUKRAN. I would like to thank the chairperson of my committee, Dr. Martin B. Main for his encouragement, support, guidance and sense of humor – all of which enabled me to attain a Master of Science Degree from the University of Florida’s Department of Wildlife Ecology and Conservation. His passion and commitment to his work is a true inspiration. I would also like to thank my other committee members, Dr. Mark Hostetler and Dr. Mike Moulton for their advice and expertise. The support staff at the Department of Wildlife Ecology and Conservation deserves a special thank you; their helpfulness, dedication and team-work is commendable. I thank Islamorada Village of Islands for the partial funding of my research. Additionally, I would like to thank the staff and volunteers (especially Donna Sprunt) of the Windley Key Fossil Reef Geological State Park and the staff at the Keys Marine Laboratory for their helpfulness during the fieldwork portion of my research. I would like to express a special thanks to the Hennig Family…Markus, Melissa and Robert have been extremely supportive especially during my last semester as a graduate student. I am grateful for their encouragement, friendship and proficiency at making a great cup of coffee (but mostly for their encouragement and friendship). 4 TABLE OF CONTENTS page ACKNOWLEDGMENTS ...............................................................................................................4 LIST OF TABLES...........................................................................................................................6 LIST OF FIGURES .........................................................................................................................7 ABSTRACT.....................................................................................................................................8 CHAPTER 1 INTRODUCTION ..................................................................................................................10 2 METHODS.............................................................................................................................13 Study Area ..............................................................................................................................13 Assessment of Hammock Habitat...........................................................................................14 Bird Surveys ...........................................................................................................................15 Analysis ..................................................................................................................................17 3 RESULTS...............................................................................................................................27 Assessment of Hammock Habitat...........................................................................................27 Bird Surveys ...........................................................................................................................29 4 DISCUSSION.........................................................................................................................45 Assessment of Hammock Habitat...........................................................................................45 Bird Surveys ...........................................................................................................................46 Conservation Implications......................................................................................................51 LITERATURE CITED ..................................................................................................................55 BIOGRAPHICAL SKETCH .........................................................................................................61 5 LIST OF TABLES Table page 2-1 Number and description of 20-m, fixed-radius point count bird survey sites including hammock size, conservation status, and location and description (MM = mile marker on highway US-1)..............................................................................................................19 2-2 Description and quantification (mean and s.d., median and range) of habitat variables measured at point count locations (20-m fixed radius) where bird surveys were conducted. .................................................................................................................23 2-3 Foraging guild and life history descriptions ......................................................................24 3-1 Total amount (ha) of hammock habitat including percent of total in protected status by island in the Florida Keys as of 2004............................................................................34 3-2 Partially protected hammock habitat patches in the Florida Keys including total number of patches and area (ha) in protected and unprotected status by island and patch size category (ha) of 2004 (islands that did not contain partially protected patches were excluded from this table)..............................................................................35 3-3 Avian species detected during point count surveys including standard abbreviations, common and scientific names, life history and breeding status, and foraging guild designations........................................................................................................................36 3-4 Influence of measured habitat variables on species presence or absence from analyses with general linear models (data represent p-values). A negative p-value indicates an inverse relationship between the habitat variable and species presence. .....40 3-5 Influence of measured habitat variables on life history and foraging guilds from general linear model analyses with zero-inflated Poisson regression model (data represent p-values). A negative p-value indicates an inverse relationship between the habitat variable and species presence. ...............................................................................41 3-6 Hammock habitat variables for birds that lacked sufficient data for statistical analyses. Data reflect the range of percent cover (smallest to largest) for PCT_HAM, PCT_CAN and HAM+CAN measurements where birds were observed. .........................42 6 LIST OF FIGURES Figure page 2-1 Geologic delineation of the Florida Keys by substrate. ...................................................25 2-2 Delineation of Upper Keys (consistent with Bancroft et al. 1995) study area, Lower Keys study area and extent of avian surveys. ....................................................................26 3-1 Area (ha) of tropical hardwood hammock habitat patches by patch size (ha) category and protected status in the Florida Keys in 2004 (number of habitat patches provided above each bar). .................................................................................................................44 7 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science STATUS AND USE OF TROPICAL HARDWOOD HAMMOCKS AND FORESTED RESIDENTIAL AREAS AS HABITAT FOR RESIDENT AND NEOTROPICAL MIGRATORY BIRDS IN THE FLORIDA KEYS By Annisa Karim December 2007 Chair: Martin B. Main Major: Wildlife Ecology and Conservation The challenges of migration are immense and many avian species rely on stopover areas to rest and refuel before continuing migration. The availability and location of stopover habitat is vital to migratory species, and the loss of suitable stopover habitats has been implicated in the decline of migratory populations. Tropical hardwood hammocks in the Florida Keys are used by both resident and Neotropical migratory birds; however, anthropogenic activities in and around hammocks have resulted in the conversion of many of these forests to other urban uses. As a result, habitat loss and fragmentation have reduced suitable habitat. I used a Geographic Information Systems approach to quantify amount and status (protected/unprotected) of hammock forest patches in the Keys. More than 30% of hammock habitat in the upper Keys had been lost to deforestation from 1991 to 2004. Total remaining hammock habitat in the Florida Keys as of 2004 was 3,712 ha, of which 1,962 ha (53%) was located in the upper Keys, and 1,750 ha (47%) was located in the lower Keys. Of the remaining hammock habitat, approximately 37% remained unprotected throughout the Keys (46% and 27% in the upper and lower Keys, respectively). I conducted bird point counts at 86 survey sites in the northern Keys during March-May 2004 and 2005. Survey locations were established in both hammock