Do recreationists hinder birdsâ•Ž abilities to acquire fat during migra

78 Pages·2015·2.42 MB·English

by  Laura Marsh

RELATIONSHIP BETWEEN HUMAN INTRUSION AND AVIAN BODY MASS:
DO RECREATIONISTS HINDER BIRDS’ ABILITIES
TO ACQUIRE FAT DURING MIGRATION?

By
Laura Kathryn Marsh

David A. Aborn Jennifer N. Boyd
Associate Professor of Biological and Associate Professor of Biological and
Environmental Sciences Environmental Sciences
(Committee Chair) (Committee Member)

Hope M. Klug
Assistant Professor of Biological and
Environmental Sciences
(Committee Member)
RELATIONSHIP BETWEEN HUMAN INTRUSION AND AVIAN BODY MASS:
DO RECREATIONISTS HINDER BIRDS’ ABILITIES
TO ACQUIRE FAT DURING MIGRATION?

By
Laura Kathryn Marsh

A Thesis Submitted to the Faculty of the University of Tennessee
at Chattanooga in Partial Fulfillment of the Requirements
of the Degree of Master’s of Science: Environmental Science

The University of Tennessee at Chattanooga
Chattanooga, Tennessee

August 2015

ii
Copyright © 2015
By Laura Kathryn Marsh
All Rights Reserved
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ABSTRACT

Many North American landbirds undergo biannual migration, which is energetically costly.
Quality stopover sites are crucial to avian survival, as they provide opportunities to quickly replenish fat
stores, rest, and avoid predation. One component of habitat quality that is often overlooked is the level of
pedestrian activity, which birds interpret as potential predators. If intrusion levels are high, birds will
flush readily and may not adequately restore energy reserves, which hinders successful migration. I
compared body mass index between birds at different intrusion levels, testing the hypothesis that birds
near continuous intrusion are less capable of replenishing body fat. Results between migratory guilds
indicate long-distance migrants require areas of low intrusion to sufficiently acquire fat stores. In contrast,
resident species are able to replenish body mass despite human intrusion. Since Neotropical migrants
show increased sensitivity to human presence, conservation measures should focus on reducing pedestrian
activity for quality stopover habitats.

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DEDICATION

I would like to dedicate this work to my unborn son. It has been a miracle feeling him grow, kick,
and dance inside the womb, and his impending birth has given me the final motivation to finish this work.

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ACKNOWLEDGEMENTS

I owe a huge debt of gratitude to so many people. First and foremost, my advisor, Dr. David
Aborn, has provided me with endless guidance, insight, and patience during this process. Not only did he
assist my work in the field, but he has mentored me throughout this process. He has been invaluable in his
knowledge, encouragement, and forgiveness. Thank you so much. I also thank Drs. Jennifer Boyd and
Hope Klug for being willing to step into my committee and contribute a plethora of knowledge in a short
period of time. Their comments and revisions were vital in the timely completion of my thesis. I also
acknowledge Drs. Loren Hayes and Mark Schorr for their contributions to my work. I thank the City of
Chattanooga for allowing me to use Greenway Farms as a study site, and the University of Tennessee at
Chattanooga Office of Partnerships and Sponsored Programs for awarding me a Provost Student Research
Award to help fund my thesis project. The faculty, staff, graduate peers, and friends in the Biological and
Environmental Sciences Department have poured out continuous assistance: I wish I had room to list you
all by name! I also deeply appreciate my parents for their lifelong support: they raised me to be
inquisitive, hard-working, and motivated, which are necessary skills for a researcher. Finally, I want to
thank my husband, who has supported and encouraged me in all of our marriage, but especially during my
busy time as a graduate student.

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TABLE OF CONTENTS

ABSTRACT iv

DEDICATION v

ACKNOWLEDGEMENTS vi

LIST OF TABLES ix

LIST OF FIGURES x

LIST OF ABBREVIATIONS xi

CHAPTER

I. INTRODUCTION 1

1.1 Migration 1
1.2 Migratory Stopover 2
1.3 Impacts of Urbanization 3
1.4 The Influence of Human Intrusion on Wildlife 5
1.4.1 Type of Activity 7
1.4.2 Predictability 7
1.4.3 Frequency and Magnitude 8
1.4.4 Timing 9
1.4.5 Location 9
1.5 Avian Responses to Intrusion 10
1.5.1 Guild Specific Responses 10
1.5.2 Levels of Impacts 11
1.5.3 Stress Responses 13

II. THESIS RESEARCH 15

2.1 Research Questions 15
2.2 Research Design and Methods 18
2.2.1 Study Site 18
2.2.2 Pedestrian Rate 19
2.2.2.1 Stationary Observation 20
2.2.2.2 Passive Observation 20
2.2.3 Mist Net Setup 21
2.2.4 Body Condition 21
2.2.5 Food Sampling and Vegetation Structure 22
2.3 Data Analysis 23
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2.3.1 Food Sampling and Vegetation Structure 23
2.3.2 Body Mass Index 24
2.3.3 Data Transformation 26
2.3.4 Parametric Statistical Analysis 27
2.3.5 Non-Parametric Analysis 27

III. RESULTS 28

3.1 Overall Results 28
3.1.1 Sampling Effort, Diversity, and Similarity 28
3.2 Site Differences 29
3.2.1 Intrusion Level 29
3.2.2 Food Availability 29
3.2.3 Arthropod Composition 30
3.2.4 Vegetation Structure 32
3.3 Body Condition Differences 32
3.3.1 All Species 32
3.3.1.1 Fall 33
3.3.1.2 Spring 37
3.4 Family Analyses 39
3.4.1 Family Turdidae – Thrushes 39
3.4.1.1 Fall 39
3.4.1.2 Spring 41
3.4.2 Family Parulidae – Wood Warblers 42
3.4.2.1 Fall 43
3.4.2.2 Spring 45
3.5 Species Analyses 47
3.5.1 Northern Cardinal 47
3.5.1.1 Fall 47
3.5.1.2 Spring 47
3.5.2 Hooded Warbler 47

IV. DISCUSSION 49

4.1 Site Differences 49
4.2 All Species 50
4.3 Family and Species Analyses 54
4.3.1 Turdidae 54
4.3.2 Parulidae 55
4.3.3 Northern Cardinal 56
4.3.3 Hooded Warbler 57
4.4 Conclusion 57
4.4.1 Conservation Implications 58
4.4.2 Future Work 58

REFERENCES 60

VITA 67
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LIST OF TABLES

1 Total birds caught between Sites, Years, Seasons, and Migratory Guilds. LDM = Long-
distance Migrants, SDM = Short-distance Migrants, RES = Residents 28

2 Arthropod totals and proportions between locations (Greenway and Bluff) and years (2013
and 2014). Percentages are based on proportions of the grand total of individuals
collected in the study 30

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LIST OF FIGURES

1 Two study sites located on the Greenway Farms land in Hamilton County, Tennessee.
Greenway site has high intrusion (top, pink). Bluff site has low intrusion (bottom,
orange) 19

2 Arthropod composition at Greenway and Bluff sites for 2013 31

3 Arthropod composition at Greenway and Bluff sites for 2014 32

4 Mean Rank SMI for Migratory Guild (long-distance, short-distance, and resident)
between Greenway and Bluff sites observed during the fall season for 2013 and
2014 study periods. Whiskers indicate +/- 1 standard error 34

5 Mean Rank SMI for Greenway and Bluff locations between years (2013 and 2014) for fall
season. Whiskers indicate +/- 1 standard error 35

6 Mean Rank SMI for Migratory Guild (long-distance, short-distance, and resident)
between years (2013 and 2014) during the fall season. Whiskers indicate +/- 1
standard error 36

7 Mean Rank SMI for Migratory Guild (long-distance, short-distance, and resident)
between Greenway and Bluff sites observed during the spring season for 2013 and 2014
study periods. Whiskers indicate +/- 1 standard error 38

8 Mean Rank SMI for Migratory Guild (long-distance and short-distance) of Thrushes (family
Turdidae) between Greenway and Bluff sites observed during the fall season for 2013
and 2014 study periods. Whiskers indicate +/- 1 standard error 40

9 Mean Rank SMI of Thrushes (family Turdidae) for Greenway and Bluff sites between
years (2013 and 2014) observed during the spring season. Whiskers indicate +/- 1
standard error 42

10 Mean Rank SMI of Wood Warblers (family Parulidae) for Greenway and Bluff sites
between years (2013 and 2014) observed during the fall season. Whiskers indicate +/- 1
standard error 44

11 Mean Rank SMI of Wood Warblers (family Parulidae) for Greenway and Bluff sites
between years (2013 and 2014) observed during the spring season. Whiskers indicate
+/- 1 standard error 46

12 Mean Rank SMI of Hooded Warbler (Setophaga citrina) for Greenway and Bluff sites
between years (2013 and 2014) observed during the fall season. Whiskers indicate
+/- 1 standard error 48
x