The Effects of Human Disturbance on Birds in Bastrop State Park (BSP) in Central Texas in 1998 and 1999
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Texas A&M Repository THE EFFECTS OF HUMAN DISTURBANCE ON BIRDS IN BASTROP STATE PARK A Dissertation by HEIDI ANN MARCUM Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY August 2005 Major Subject: Wildlife and Fisheries Sciences © 2005 HEIDI ANN MARCUM ALL RIGHTS RESERVED THE EFFECTS OF HUMAN DISTURBANCE ON BIRDS IN BASTROP STATE PARK A Dissertation by HEIDI ANN MARCUM Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Approved by: Chair of Committee, Keith A. Arnold Committee Members, Nova J. Silvy William E. Grant David Scott Head of Department, Robert D. Brown August 2005 Major Subject: Wildlife and Fisheries Sciences iii ABSTRACT The Effects of Human Disturbance on Birds in Bastrop State Park. (August 2005) Heidi Ann Marcum, B.S., Tarleton State University; M.S., Baylor University Chair of Advisory Committee: Dr. Keith A. Arnold With rapidly disappearing natural areas due to development and fragmentation, public lands provide important habitat for birds. However, the increasing use of public lands for recreation may decrease the value of these areas for bird use. Human disturbance can damage birds in many ways, including disrupting foraging or social behavior, increasing nest predation, interfering with parent-offspring and pair bonds, increasing nesting failures, and reducing the viability of fledglings. Additionally, birds may perceive humans as predators and leave an area, and the resulting decline in species abundance resembles the effects of habitat loss. Increased human outdoor activity has created the need for information regarding the effects of human disturbance on birds. I investigated the effects of human disturbance on birds in Bastrop State Park (BSP) in central Texas in 1998 and 1999. A wide variety of people use much of BSP, and many areas within the park experience significant amounts of disturbance from people and vehicles, particularly in campgrounds. I evaluated the effects of various types of human disturbance on the presence of 20 avian species, including seven neotropical migratory species. Brown-headed Cowbird (Molothrus ater), Mourning Dove (Zenaida iv macroura), Carolina Wren (Thryothorus ludovicianus), and Summer Tanager (Piranga rubra), were sensitive to human presence, and Blue Jays (Cyanocitta cristata), and Downy Woodpeckers (Picoides pubescens) occurred in lower abundances in sites with higher numbers of vehicles. However, other species (e.g., American Crow [Corvus brachyrhynchos], Black-and-white Warbler [Mniotilta varia], Pileated Woodpecker [Dryocopus pileatus], Red-eyed Vireo [Vireo olivaceus], Ruby-throated Hummingbird [Archilochus colubris], White-eyed Vireo [Vireo griseus], and Yellow-billed Cuckoo [Coccyzus americanus]) tolerated humans, vehicles, or both. Neotropical migratory species did not show higher sensitivity to disturbance when compared to resident species, and forest interior species were not more sensitive than edge species. My results indicate that some species, including migrants, can become habituated to human presence in protected areas with low harassment and low-intensity, predictable disturbances. Management recommendations for BSP include protecting habitat, minimizing human disturbance in some areas, providing buffer zones between human- dominated zones and sites containing vulnerable species, and softening edges in campgrounds. v ACKNOWLEDGEMENTS I thank Dr. Keith Arnold for his dedication and devotion to excellence in scholarship, and for his unwavering faith in my abilities to earn this degree. Additionally, I offer thanks to my dissertation committee, who worked so willingly with me: Drs. William E. Grant, Nova J. Silvy and David Scott. They were always generous with their help, and I value their guidance and professionalism. I would like to thank Baylor University for giving me the time off so I could pursue my degree, without which I could not have advanced my career. I am grateful for my students who spent countless hours in the field with me, sharing my enthusiasm for this project. I thank the field technicians for their hard work during often brutal summer heat in rough conditions. I would like to acknowledge Dr. Kevin J. Gutzwiller, who was instrumental in urging me to strive for loftier goals, and who had faith in my abilities from the beginning. I am also indebted to the Texas Parks and Wildlife Department (Permit # 33-99), for allowing unlimited access to Bastrop State Park and for the considerable expertise and help of the staff. Finally, I thank my family, who supported me through the long process of my education. My love and gratitude go to my husband, Greg, who always supported my endeavors, and took the responsibility of running the household so I could pursue my degree. I am indebted to my sister, Mary, who did untold hours of chores that gave me the time to work on this project, and who provided great advice. Finally, I am ever grateful to my parents, who gifted me with a love of learning. vi TABLE OF CONTENTS Page ABSTRACT...................................................................................................................... iii ACKNOWLEDGEMENTS ............................................................................................... v TABLE OF CONTENTS.................................................................................................. vi LIST OF FIGURES........................................................................................................... ix LIST OF TABLES ............................................................................................................. x INTRODUCTION.............................................................................................................. 1 Review of the Literature................................................................................................. 4 Human intrusion......................................................................................................... 5 Humans as disturbance............................................................................................... 6 Roads as disturbance .................................................................................................. 7 Vulnerability to disturbance ....................................................................................... 8 Disturbance effects on bird behavior.......................................................................... 9 Disturbance effects on nest predation ...................................................................... 11 Humans as predators ................................................................................................ 12 Habituation............................................................................................................... 13 The role of state parks in species protection ............................................................ 14 METHODS....................................................................................................................... 16 Bastrop State Park ........................................................................................................ 16 Study site.................................................................................................................. 16 Vegetative and trail characteristics of BSP .............................................................. 19 Field Techniques .......................................................................................................... 20 Point count placement .............................................................................................. 20 Bird census ............................................................................................................... 22 Human disturbance................................................................................................... 24 Statistical Analysis ....................................................................................................... 28 Data description........................................................................................................ 28 Species presence vs. absence ................................................................................... 29 Species presence in control, trail, road, and campground sites................................ 31 vii Page RESULTS......................................................................................................................... 32 Disturbance at BSP....................................................................................................... 32 Disturbance, 1998..................................................................................................... 32 Disturbance, 1999..................................................................................................... 35 Spearman rank correlation coefficients.................................................................... 37 Differences in disturbance between control, trail, road, and campground sites....... 39 Bird Species at BSP...................................................................................................... 43 Avian species, 1998.................................................................................................