DIVING DUCK ABUNDANCE AND DISTRIBUTION ON LAKE ST. CLAIR AND WESTERN LAKE ...

127 Pages·2012·3.82 MB·English

DIVING DUCK ABUNDANCE AND DISTRIBUTION ON LAKE ST. CLAIR AND
WESTERN LAKE ERIE

By

Brendan T. Shirkey

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

Master of Science

Fisheries and Wildlife

2012
ABSTRACT

DIVING DUCK ABUNDANCE AND DISTRIBUTION ON LAKE ST. CLAIR AND
WESTERN LAKE ERIE

By

Brendan T. Shirkey

Lake St. Clair and western Lake Erie are important migration staging areas for
diving ducks including canvasbacks (Aythya valisineria), redheads (Aythya americana),
and lesser and greater scaup (Aythya affinis and Aythya marila). The Michigan DNR has
censused diving ducks on the United States portion of Lake St. Clair dating back to 1983,
but in 2010 traditional surveys were expanded to cover all of Lake St. Clair and portions
of western Lake Erie and distance sampling techniques were adopted in an effort generate
statistical estimates of abundance. Furthermore, GPS locations were recorded for all
flocks allowing for the development of spatial models to investigate the effects of
environmental and anthropogenic variables on diving duck distribution. We found
distance sampling techniques to be a viable option for estimating diving duck abundance
as long as flock size is accounted for as a covariate affecting the detection function, and
we were able to apply distance sampling methods to both spring and fall migration.
Human disturbance (i.e., presence of boats) and environmental variables (i.e., water depth
and plant species richness) were predictive of diving duck occurrence. Differences
between spring and fall abundance and variables predictive of spring and fall occurrence
may indicate diving ducks are adopting different landscape use strategies in fall
compared to spring, and this may have significant implications for wetland conservation
planning.
DEDICATION

This work is dedicated to my parents, Tom and Wanda Shirkey. Without my
mother’s patience and my father’s guidance, I never would have learned the true value of
a life spent outdoors. There is no doubt that hunting and fishing fostered the qualities
that make me who I am, and it was their appreciation for all living things that drove me to
pursue a career in conservation.

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ACKNOWLEDGEMENTS

First, I would like to thank my parents, Tom and Wanda, and my sister Erin
because without their support I never would have finished college in the first place. I
would also like to thank the punter’s and staff at the Winous Point Marsh Conservancy
not only for sharing in many of my most memorable hunting experiences but also for
teaching me there is much to be learned outside the classroom.
I thank my funding sources such as The Upper Mississippi River Great Lakes
Region Joint Venture, The Michigan Division of Natural Resources, Michigan State
University, The Safari Club and the Winous Point Marsh Conservancy. I will forever be
indebted to all of these great organizations for their support. I thank John Simpson, Dave
Sherman, and Jacob Gray for always lending an ear and some words of guidance to assist
in making this project what I hope is a valuable contribution to the waterfowl community.
I thank my fellow observers, Joe Robison, Ernie Kafcas, Mike Wegan, Ryan Boyer,
Dusty Arsenoe, and Howie Singer for all the long and sometimes uneventful hours they
spent in an airplane with me. I thank Dr. David Williams for his GIS support and Dr.
Andrew Finley for his spatial statistics expertise. I also thank Dr. Dave Luukkonen and
Dr. Scott Winterstein not only for the statistical support and guidance, but also for forcing
me to develop the skills necessary to become a professional in wildlife management. I
thank my pilots Derek Deruiter and Bob Anton; without them none of this work would
have been possible.
Lastly and most importantly, I thank my wife Kelly. Without her never ending
patience, love, and understanding, this work would never have been completed. She
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volunteered to listen to countless practice presentations and was always willing to listen
to me talk about ducks, which I assume must be rather boring for normal folks.

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TABLE OF CONTENTS
LIST OF TABLES…………………………………………………………………viii
LIST OF FIGURES………………………………………………………………….x
CHAPTER 1
Introduction: Monitoring Diving Ducks During Migration on Lake St. Clair
and Western Lake Erie………………………………………………………………..1
Importance of Lake St. Clair and western Lake Erie…………………………1
Threats posed to diving ducks on the lower Great Lakes……………………..2
Importance and challenges of monitoring diving ducks during migration…...6
Research objectives and thesis organization………………………………….8
Literature Cited………………………………………………………………10

CHAPTER 2
Estimating Diving Duck Abundance During Migration Using Distance
Sampling Techniques………………………………………………………..15
Introduction………………………………………………………………….15
Study area and methodology………………………………………………...17
Results……………………………………………………………………….23
Discussion …………………………………………………………………...33
Management Implications…………………………………………………..38
Appendices…………………………………………………………………..40
Literature Cited……………………………………………………………...64

CHAPTER 3
Spatial Modeling of Diving Duck Distributions on Lake St. Clair and Western Lake
Erie…………………………………………………………………….......................68
Introduction…………………………………………………………………..68
Study area and methodology…………………………………………………71
Historical survey methods……............................................................71
Current survey methods………………………………………………72
Results………………………………………………………………………...76
Historical survey data………………………………………………...76
Current survey data…………………………………………………...77
Discussion…………………………………………………………………….90
Management Implications…………………………………………………….94
Appendices…………………………………………………………………....97
Literature cited………………………………………………………………..103

CHAPTER 4
Summary……………………………………………………………………………….107
Introduction……………………………………………………………………107
Research and Management Implications of Abundance Estimation and Spatial
Modeling Techniques for Diving Ducks on Lake St. Clair and Western
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Lake Erie……………………………………………………………………….108
Literature Cited………………………………………………………………...115

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LIST OF TABLES

Table 1. Pooled survey effort for Lake St. Clair, western Lake Erie, canvasbacks,
redheads, and scaup during each of the 4 migration time frames……………24

Table 2. Survey date, truncation distance (w), number of observations before and after
truncation (n), model selected for abundance estimation, p-value obtained from
chi-square goodness-of-fit test, detection probability, coefficient of variation for
the abundance estimate and model weight for individual surveys conducted over
Lake St. Clair and western Lake Erie………………………………………..27

Table 3. Area or species of interest, number of observations before and after truncation
(n), model selected for analysis, p-value from chi-square goodness-of-fit test,
detection probability, coefficient of variation for abundance estimates and model
weight for (a) Fall 2010, (b) Spring 2011, (c) Fall 2011, and (d) Spring 2012
pooled analyses………………………………………………………………28

Table 4. Survey date, 95% lower confidence limit (N LCL), abundance estimate (N), and
95% upper confidence limit (NUPL) for all individual surveys conducted on Lake
St. Clair and western Lake Erie during the two year study. Confidence limits
obtained for all surveys that included cluster size as a covariate were estimated
via the bootstrap option in Distance 6.0………………………………………30

Table 5. Survey date, ocular estimate, distance based estimate, and area covered for
flocks containing > 10,000 individuals observed during the two year study…32
Table 6. Candidate models examined prior to selection of models used to perform (a)
individual surveys and (b) pooled analyses. We did not consider models for either
set of analyses that did not include clustersize as a covariate except for the default
hazard rate and half normal models because we were uncomfortable with the
regression method for estimating average flock size. We also did not include
observer as a covariate for pooled analyses because we had very few observations
(>10) per area or species of interest for some observers………………………..42
Table 7. Survey date, the number of censused large groups (>10,000 birds), and the
ocular estimate of the number of individuals contained in those large groups….63
Table 8. Migration period and corresponding percent of sites occupied by diving ducks
and recreational boats on Lake St. Clair and western Lake Erie. Total sites on
Lake St. Clair were 820 in Fall 2010 and 1025 in all other migration periods, and
total sites on Lake Erie were 448 in Fall 2010 and 560 in all other migration
periods (see Appendix A for % cells occupied by individual date)……………77

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Table 9. Migration season, survey date, 50% Bayesian quantiles (50% b), and empirical
standard deviations (SD) for the intercept, presence of boats, distance to shore,
water depth, and plant species richness covariates from hierarchical spatial
models predicting diving duck presence on Lake St. Clair (* denotes statistical
significance based on Bayesian criterion where the 95% credibility intervals for
the posterior distributions of the parameters did not include 0; see Appendix B for
Bayesian credibility intervals and parameter estimates for the spatial random
effects)………………………………………………………………………83

Table 10. Averaged Bayesian parameter estimates ( B ˆ ) and associated 95% confidence
limits from hierarchical spatial models predicting diving duck occurrence for Fall
2010, Spring 2011, Fall 2011, and Spring 2012 on Lake St. Clair. Confidence
limits were calculated with empirical standard deviations and methods outlined by
Thompson (1992) for linear combinations of random variables……………..84

Table 11. Survey date and corresponding percent of sites occupied by diving ducks and
recreational boats on Lake St. Clair and western Lake Erie. The total number of
sites on Lake St. Clair was 205 and the total number on Lake Erie was 112….98

Table 12. 2.5 %, 50%, and 97.5% Bayesian quantiles for the intercept term, the 4 non-
spatial covariates (boats, distance to shore, water depth, and plant species
richness), the spatial random effects (Phi), and the variance of the spatial random
2
effects (Sigma ). All hierarchical models were generated in the spBayes package
for the statistical software R and were organized by migration season a) Fall 2010,
b) Fall 2011, c) Spring 2011, and d) Spring 2012……………………………99
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LIST OF FIGURES

Figure 1. Map of Lake St. Clair and western Lake Erie diving duck survey area with east-
west survey transects shown as solid lines. For interpretation of the references to
color in this and all figures, the reader is referred to the electronic version of this
thesis……………………………………………………………………………19

Figure 2. Illustration of survey area beneath the aircraft showing 5 distance categories
established after the first field season and the non-surveyed area directly below
the plane that was blocked from view by the aircraft’s floats. Distance categories
include: 1) 0-50 m, 2) 51-125 m, 3) 126-225 m, 4) 226-425 m, and 5) >425
m…………………………………………………………………………….20

Figure 3. Estimates of diving duck-use-days and 95% CI’s by lake and migration season
with means calculated from pooled abundance estimates divided by the number of
surveys (5) and multiplied by the number of days in the migration period (42)...31

Figure 4. Estimates of diving duck-use-days and 95% CI’s by species and migration
season with means calculated from pooled abundance estimates divided by the
number of surveys (5) and multiplied by the number of days in the migration
period (42)……………………………………………………………………….31

Figure 5. Illustration of the effects of flock size when included as a covariate in the
detection function. As flock size increases detection probability remains higher at
greater distances from the transect line………………………………………….35

Figure 6. Detection probability as a function of average wind speed recorded by the
observers on the day of the survey……………………………………………...39
Figure 7. Model fit images for all individual surveys (a-t) conducted over Lake St. Clair
and western Lake Erie during the two year study. Detection probability is on the
y-axis and distance (m) from the transect is on the x-axis. Binned distance data is
shown in blue and the detection function fit to that data by program Distance is
shown in red, and each blue bar represents the observed flock density divided by
the expected flock density of the first distance category……………………….43
Figure 8. Model fit images for all pooled analyses (a-t) conducted over Lake St. during
the two year study. Detection probability is on the y-axis and distance (m) from
the transect is on the x-axis. Binned distance data is shown in blue and the
detection function fit to that data by program Distance is shown in red, and each
blue bar represents the observed flock density divided by the expected flock
density of the first distance category…………………………………………….53

x