Noonburg, Erik G.

For over a decade, researchers at Harbor Branch Oceanographic Institute have conducted
surveys of the population of bottlenose dolphins, Tersiops truncatus, in Indian River Lagoon
along the east coast of Florida. I have constructed a detailed 4-stage population model using the
statistical program R. The model is used as a tool for conducting a viability analysis that projects
the dolphin population into the future by analyzing the relationship between birth, calf survival
and adult survival rates. The model also includes a power analysis, which compares survey
frequency to expected confidence intervals in estimating abundance. The model shows a strong
chance of viability over a 50 year time span, primarily due to the large population size of
approximately 700 adult dolphins. The population is vulnerable to long periods of decline if
birth, calf or adult survival rates fall below certain thresholds. The sensitivity analysis, based on
the partial derivatives of the eigenvalue with respect to each matrix element, shows that the
population is most sensitive to changes in adult survival, followed by birth rate and calf survival.
Overall, the model simulates the future impacts of demographic change, and thereby provides a
tool for conservation efforts.

As top-level piscivores, Bald Eagles are a compelling subject for the study of
territory dynamics and are highly representative of the distinctive suite of avian species
that occupy Florida Bay. Despite successful recovery of Bald Eagles (Haliaeetus
leuocephalus) throughout the species range, the population breeding within Florida Bay
has not mirrored this trend. Beginning in the late 1980s, Florida Bay has suffered in its
capacity to support species diversity and abundance as a result of extreme changes in
hydrology related to altered flows of incoming freshwater. In fact, Bald Eagle territory
use in Florida Bay has declined by as much as 43% as year to year variation and
sensitivity to transitions between territory states have increased. Florida Bay’s
populations of other large, conspicuous fish-eating birds, including Ospreys, Great White
Herons, Roseate Spoonbills, and Reddish Egrets each exhibit a similar pattern of decline. The effects of environmental degradation throughout Florida Bay are magnified at higher
trophic levels. The negative trend in territory occupancy is most pronounced in southeast
Florida Bay whereas effects on territory occupancy in the northwest are minimal. The
presence of spatial patterns in territory occupancy, despite regionally available breeding
birds, suggests that individuals are evaluating differences in habitat quality for which
certain territories are no longer considered viable. Building on our current understanding
of the health of this population of Bald Eagles, we have successfully implemented
modeling approaches that identify key territory breeding decisions. Loss of early
breeding season activity (occupied and active territories) despite maintaining high
breeding success indicates that changes in territory dynamics are the result of a failure to
breed and not a reproductive failure. As such, future conservation actions should
promote early breeding season activity (decisions by breeding pairs to initiate nesting) in
areas of Florida Bay that were historically occupied but are now abandoned.

For over a decade, researchers at Harbor Branch Oceanographic Institute (HBOI)
have conducted surveys of the bottlenose dolphin (Tursiops truncatus) population of
Indian River Lagoon (IRL) in Florida. I have constructed a 4-stage population model
using the statistical program R. The model is used to conduct a viability analysis by
analyzing the relationship between birth, calf and adult survival rates. The power
analysis compares survey frequency to expected confidence intervals in estimating
abundance. The sensitivity analysis shows that the population is most sensitive to
changes in adult survival, followed by birth rate and calf survival. The model shows a
strong chance of viability over a 50 year time span. The population is vulnerable to long
periods of decline if birth, calf or adult survival rates fall below certain thresholds.
Overall, the model simulates the future impacts of demographic change, providing a tool
for conservation efforts.

In south Florida, the Greater Everglades ecosystem supports sixteen species of
wading birds. Wading birds serve as important indicator species because they are highly
mobile, demonstrate flexible habitat selection, and respond quickly to changes in habitat
quality. Models that establish habitat relationships from distribution patterns of wading
birds can be used to predict changes in habitat quality that may result from restoration
and climate change. I developed spatio-temporal species distribution models for the
Great Egret, White Ibis, and Wood Stork over a decadal gradient of environmental
conditions to identify factors that link habitat availability to habitat use (i.e., habitat
selection), habitat use to species abundance, and species abundance (over multiple scales)
to nesting effort and success. Hydrological variables (depth, recession rate, days since
drydown, reversal, and hydroperiod) over multiple temporal scales and with existing
links to wading bird responses were used as proxies for landscape processes that influence prey availability (i.e., resources). In temporal foraging conditions (TFC)
models, species demonstrated conditional preferences for resources based on resource
levels at differing temporal scales. Wading bird abundance was highest when prey
production from optimal periods of wetland inundation was concentrated in shallow
depths. Similar responses were observed in spatial foraging conditions (SFC) models
predicting spatial occurrence over time, accounting for spatial autocorrelation. The TFC
index represents conditions within suitable depths that change daily and reflects patch
quality, whereas the SFC index spatially represents suitability of all cells and reflects
daily landscape patch abundance. I linked these indices to responses at the nest initiation
and nest provisioning breeding phases from 1993-2013. The timing of increases and
overall magnitude of resource pulses predicted by the TFC in March and April were
strongly linked to breeding responses by all species. Great Egret nesting effort and
success were higher with increases in conspecific attraction (i.e., clustering). Wood Stork
nesting effort was closely related to timing of concurrently high levels of patch quality
(regional scale) and abundance (400-m scale), indicating the importance of a multi-scaled
approach. The models helped identify positive and negative changes to multi-annual
resource pulses from hydrological restoration and climate change scenarios, respectively.