Waterfowl studies on the SRS have focused on three primary
areas: basic ecological studies of both the locally breeding
waterfowl populations and the much larger visiting winter
populations, studies of the patterns of abundance and distribution
of waterfowl on the SRS, and environmental contaminant uptake
and cycling. Among the techniques commonly employed in these
studies have been the use of artificial nest boxes for the
cavity-nesting Wood Duck, aerial censusing of winter waterfowl
populations, large-scale trapping and banding efforts, and
gamma-spectroscopy.
Long-term study of breeding
Wood Ducks
Wood Ducks are second only to Mallards in numbers of waterfowl
harvested along the Atlantic Flyway, with an average of
286,000 birds killed annually between 1961 and 1986. Since
the early 1970s, breeding Wood Ducks using nest boxes located
throughout the SRS have been studied extensively. This research
has pro-vided valuable in-formation on the population dynamics
of Wood Ducks. Annual adult female survival on the SRS,
estimated from capture-recapture data, averages 59% and
is comparable to that from other areas of the Southeast.
The breeding female Wood Duck population using long-term
monitored SRS nest boxes stabilized at about 110 individuals
during the latter 1980s and early 1990s. Production of Wood
Ducks from nest boxes, however, is known to be only a fraction
of that occurring in natural cavities. Total breeding pairs
on the SRS are likely to exceed 1,000, particularly taking
into consideration the vastness of the Savannah River swamp.
- Overall, research indicates a
high degree of environmental health and productivity in
SRS wetlands occupied by Wood Ducks.
Wintering
waterfowl studies on the SRS
During
fall and winter, migrating waterfowl use the SRS extensively.
As many as 28 species of North America’s native 
waterfowl have been identified on the SRS. Aerial surveys conducted
over the SRS each winter since the early 1980s have identified
the Site’s former reactor cooling reservoirs as important
inland wintering refuges for diving ducks in the Southeast,
with maximum numbers exceeding 5,000 birds annually. These
long-term survey data have been particularly useful fordetermining
the re-sponses of waterfowl to Site-related activities.
For example:
- Addition of the
L-Lake reservoir in 1985 apparently has not yet increased
the overall carrying capacity of the SRS for wintering
waterfowl, but instead has resulted in a redistribution
of birds across the Site.
- Species
responded differently to the partial drawdown of the Par
Pond reservoir in 1991--Lesser Scaup and Ring-necked Ducks
moved to L-Lake, Bufflehead and Ruddy Ducks remained at
Par Pond, and thousands of American Coots were displaced
to unknown locations off the SRS.
Ring-necked
Duck banding efforts on the SRS from 1985 to 1995, together
with hunter-reported recoveries, have provided information
on the geographical extent and patterns of migration exhibited
by this species. As expected, most hunter recoveries took
place within the Atlantic Flyway, although some limited
exchange with the Mississippi Flyway was evident. Direct
recoveries (those occurring in the same winter as banding)
occurred in only four Southeastern states.
- South Carolina,
Georgia, Florida, and Alabama have the highest probability
that SRS-contaminated waterfowl could be harvested while
they still contain measurable radiocesium levels.
- An estimated 2.5% of
Ring-necked Ducks that visit SRS reservoirs each winter
are harvested in that same winter.
Waterfowl
contaminant studies
The
nature of DOE’s activities on the SRS warrants concern
that the Site’s abundant waterfowl resource
could become contaminated
by radionuclides or other environmental wastes and thus
threaten the health of the birds themselves or offsite hunters
who may consume them. An integral part of SREL’s waterfowl
research program has been the investigation of contaminant
accumulation by waterfowl and the associated risk this presents.
In the early 1970s, American Coots were identified as a
potential "worst case" species for radiocesium
accumulation among the Site’s aquatic birds. The subsequent
study of coot whole-body radiocesium levels at Par Pond
has indicated a long-term pattern of declining radiocesium
levels in the coot population (94% decline from 1965 to
1986), with average levels in the population declining by
one-half (i.e. the ecological half-life) every 4.3 years.
Disturbances to contaminated areas on the SRS can have unpredictable
consequences to contaminant bioavailability; the 1991 Par
Pond drawdown and its later refill dramatically affected
coot radiocesium uptake, increasing body burdens to levels
not observed since the early 1970s. Furthermore:
- Wood Duck females
and their eggs contain radiocesium and mercury at levels
comparable to those in the environment where they are
collected on the SRS.
- Wood Ducks in Steel Creek
attain equilibrium levels of radiocesium in only 17 days.
- Wood Ducks eliminate
radiocesium rapidly, losing one-half of their body burden
(i.e. the biological half-life) every six days.
- Risks to individual
hunters consuming SRS-contaminated waterfowl are low when
one takes harvest patterns, equilibrium radiocesium levels,
and elimination rates of the birds into consideration.
Waterfowl Research
on the SRS 
(back to Research Snapshots)
an
associated economic impact totaling tens of millions of
dollars in the U.S each year. This popularity with the public
has resulted in North American waterfowl being among the
world’s most thoroughly studied biota as efforts are
made to refine their management. At the Department of Energy’s
(DOE) Savannah River Site (SRS), large numbers of waterfowl
have been present since the SRS was established in the 1950s.
Here, however, waterfowl populations also represent potential
vectors of the Site’s contaminants to the offsite hunting
public, thus warranting particular scrutiny. The Savannah
River Ecology Laboratory (SREL) has conducted ecological
research focusing on SRS waterfowl for over 25 years in
an effort to gain a better understanding of the interactions
between waterfowl and environmental contaminants.