Patterns of Distribution, Abundance, and Change over Time in the Marine Bird Community of

141 Pages·2014·1.67 MB·English

by  Cushing, Daniel

AN ABSTRACT OF THE THESIS OF

Daniel A. Cushing for the degree of Master of Science in Wildlife Science presented on
June 10, 2014.

Title: Patterns of Distribution, Abundance, and Change over Time in the Marine Bird
Community of Prince William Sound, Alaska, 1989-2012.

Abstract approved:
___________ __________________________________________
Daniel D. Roby

Over recent decades, the marine ecosystems of Prince William Sound (PWS),
Alaska have experienced the concurrent effects of a major anthropogenic disturbance,
the 1989 Exxon Valdez oil spill (EVOS), and a dynamic atmospheric-oceanic
environment. Studies of top marine consumers can provide insights into processes of
ecosystem change. Using data collected during boat-based marine bird surveys in PWS
over the period 1989-2012, I used complimentary taxon- and community-centric
approaches to investigate patterns of distribution and abundance of marine birds across
space and time. In doing so, I sought to provide insight into processes that may have
affected both the birds themselves and the ecosystems of which they are a part.
I found that the marine bird community as a whole was spatially structured along
a primary onshore-offshore environmental gradient, and secondarily structured along an
estuarine-marine environmental gradient. I found two patterns of community variability
across time. The first temporal community-level pattern was likely related to sustained
rates of change in the abundance of some genera, likely caused by demographic
processes. This pattern was correlated with climate variability at time-scales of several
years to a decade. The second temporal community-level pattern was characterized by
fluctuations that correlated with climate variability at an annual time-scale, likely caused
by movements of birds between PWS and the adjacent Gulf of Alaska. I also evaluated
changes in the abundance of 18 genera of marine birds, and found that seven had
declined in abundance and three had increased over the study period; all genera that
declined were piscivorous or planktivorous. Furthermore, the rates of population change
of genera were related to their position in the onshore-offshore gradient, with the highest
rates of decline occurring in offshore-associated genera.
I also investigated spatial habitat associations and temporal changes in
abundance of a focal taxon, the seabird genus Brachyramphus. Two species within this
piscivorous, pursuit-diving genus occur in PWS, the marbled murrelet (B. marmoratus)
and the Kittlitz’s murrelet (B. brevirostris). Both are species of conservation concern, and
both experienced acute mortality in PWS caused by the EVOS. Using a statistical model
that accounted for variables affecting observed abundance across space and time, I
found that abundance decreased by more than two-thirds over the study period. I found
no evidence that rates of change differed along environmental or geographic gradients.
There was also no evidence that changes in seasonal patterns of abundance occurred.
These results are indicative of a widespread decline in the abundance of
Brachyramphus murrelets within PWS.
Taken as a whole, the results of my thesis are consistent with the hypothesis that
climate change has differentially affected nearshore and offshore components of PWS
food webs. This in turn has likely contributed to the failure of some taxa, including
Brachyramphus murrelets, to recover from population injury caused by the EVOS.
© Copyright by Daniel A. Cushing
June 10, 2014
All Rights Reserved
Patterns of Distribution, Abundance, and Change over Time in the Marine Bird
Community of Prince William Sound, Alaska, 1989-2012

by
Daniel A. Cushing

A THESIS

submitted to

Oregon State University

in partial fulfillment of
the requirements for the
degree of

Master of Science

Presented June 10, 2014
Commencement June 2015
Master of Science thesis of Daniel A. Cushing presented on June 10, 2014.

APPROVED:

Major Professor, representing Wildlife Science

Head of the Department of Fisheries and Wildlife

Dean of the Graduate School

I understand that my thesis will become part of the permanent collection of Oregon State
University libraries. My signature below authorizes release of my thesis to any reader
upon request.

Daniel A. Cushing, Author
ACKNOWLEDGMENTS

I am grateful to numerous people who have contributed to this study and to my
graduate education. This long-term study was carried out by many people over a period
of decades, and I am indebted to all of them. Dr. Steve Klosiewski and Doug Burns
designed and carried out a robust marine bird survey program in the immediate
aftermath of a major oil spill. This long-term study also depended on the hard work and
persistence of many principal investigators and project leaders over the years, including
Dr. Beverly Agler, Julian Fisher, Dr. David Irons, Steve Kendall, Dr. Kathy Kuletz, Karen
Laing, Brian Lance, Aly McKnight, Shawn Stephensen, and Kelsey Sullivan. I especially
thank Aly McKnight and Kelsey Sullivan for generously sharing their knowledge and
advice. Many observers participated in this study, and I thank all of them, particularly the
capable, dedicated, and good-spirited members of the 2010 and 2012 winter and
summer survey teams: Lisa Andreano, Eric Baker, Andy Bankert, Emily Bernhardt,
Karen Brenneman, Niels Dau, Chris Ford, Robb Kaler, Liz Labunski, Jeremy O'Donnell,
Adam Peck-Richardson, Marty Reedy, Tanya Sandberg-Diment, Ana Santos, Patty
Sullivan, Mike Walgren, Gloria Zager, and Tamara Zeller. Karen Brenneman was
instrumental in making the surveys safe, successful, and fun. Thanks also to all those
who provided us with shelter and support along the way. I am grateful to David Reggiani
of Prince William Sound Aquaculture Corporation and to the staff of the Armin F. Koernig
Hatchery for their generosity and hospitality, and also to David and Annette Janka of the
vessel Auklet and David Beam and Cedar Stark of the vessel Montague for their
exceptional service.
I am deeply grateful to my advisor, Dr. Daniel Roby, for his mentorship and
support throughout my graduate education, and for his insight. I am also deeply grateful
to Dr. David Irons for providing me with outstanding opportunities for learning and
growth, and for contributing his ideas and expertise. I thank Dr. Bruce McCune, a
member of my graduate advisory committee, for his many thoughtful contributions, and
also my Graduate Council Representative, Dr. Howard Gelberg, for his involvement. I
also thank Dr. Jim Peterson and Dr. John Van Sickle for their statistical advice and Dr.
Don Lyons for his invaluable guidance. In addition, Dr. Daniel Vernon was instrumental
in shaping my interest in a research career, and S. Kim Nelson helped form my research
interest in the ecology of marine birds.
The Prince William Sound survey program was funded by the Exxon Valdez Oil
Spill Trustee Council and by the U.S. Fish and Wildlife Service. My graduate work was
primarily funded by the U.S. Fish and Wildlife Service. I was also supported by a
Graduate Student Research Award from the North Pacific Research Board. In addition, I
received support from the Oregon State University Graduate School, College of
Agricultural Sciences, and Department of Fisheries and Wildlife, as well as the Gamma
Sigma Delta Honor Society. I am extraordinarily grateful for this support.
I am also thankful for my many friends, classmates, office-mates, and colleagues
here in Corvallis, who provided much-needed friendship, inspiration, and distraction.
Special thanks to my lab-mates Jessica Adkins, Lindsay Adrian, Kirsten Bixler, Stefanie
Collar, Nick Hatch, Tim Lawes, James Lawonn, Pete Loschl, Tim Marcella, Allison
Patterson, Adam Peck-Richardson, Dr. Yasuko Suzuki, and James Tennyson for their
ideas, assistance, and advice. And last of all, I thank my family, and especially my
wonderful wife, Amanda Cushing, for her boundless patience, love, and support.
CONTRIBUTION OF AUTHORS

Dr. Daniel Roby helped to shape the objectives of this thesis and provided
editorial review of all chapters. Dr. David Irons secured project funding, managed the
long-term seabird survey program upon which this thesis is based, and provided editorial
comments. Dr. Kathy Kuletz secured project funding, supported fieldwork, and
contributed editorial comments.
TABLE OF CONTENTS

Page
CHAPTER 1: GENERAL INTRODUCTION ................................................................ 1
LITERATURE CITED ............................................................................................... 6
CHAPTER 2: TEMPORAL CHANGE IN A SUBARCTIC MARINE BIRD
COMMUNITY LINKED TO HABITAT AND CLIMATE CHANGE ................................ 9
ABSTRACT ............................................................................................................ 10
INTRODUCTION ................................................................................................... 11
METHODS ............................................................................................................. 15
Study area .......................................................................................................... 15
Modes of atmospheric-oceanic variability ........................................................... 19
Spatial structure of the marine bird community .................................................. 20
Relationships between spatial community structure and habitat ........................ 22
Rates of change in abundance of genera ........................................................... 22
Temporal structure of the marine bird community .............................................. 23
Relationships between temporal community structure and atmospheric-oceanic
variability ............................................................................................................. 24
Relationships between temporal changes and spatial community structure ...... 25
RESULTS .............................................................................................................. 25
Spatial structure of the marine bird community .................................................. 25
Relationships between spatial community structure and habitat ........................ 26
Rates of change in abundance of genera ........................................................... 27
Temporal structure of the marine bird community .............................................. 27
Relationships between temporal structure of the marine bird community and
atmospheric-oceanic variability ........................................................................... 29
Relationships between temporal changes and spatial structure of the marine bird
community .......................................................................................................... 30
DISCUSSION......................................................................................................... 32
Spatial structure of the marine bird community and relationships between
community structure and habitat ......................................................................... 32
Changes in abundance and community composition over time, and relationships
between temporal changes and atmospheric-oceanic variability ....................... 34
Relationships between temporal changes and the spatial structure of the marine
bird community ................................................................................................... 36
Conservation implications ................................................................................... 36
LITERATURE CITED ............................................................................................. 39