Environmental Engineering Reference
In-Depth Information
0.4-0.8 ppm total DDT in osprey eggs from those areas. A crude estimate of the
bioaccumulation of total DDT from fi sh to eggs would be 0.4-0.8/<0.05 = >8 to >16.
Marginal productivity in the more polluted areas was not linked to egg concentra-
tions of DDE. DDE levels in osprey eggs from the Chesapeake Bay have decreased
tenfold from the DDT use era. “…concentrations of p,p
-DDE…in sample eggs did
not cause direct and biologically signifi cant toxic effects on osprey reproduction in
Chesapeake Bay regions of concern.”
A third study of the Delaware Bay was conducted in 2002 by Toschik et al.
(
2005
). Geometric mean DDE levels in eggs from four parts of the Bay were
0.4-1.8 ppm. Eggshells from the northern part of the Bay were 10% thinner. A few
eggs from failed nests contained more than 4 ppm DDE. The authors stated that “All
nestlings appeared in good health; no external lesions or other abnormalities were
found.” and “Additionally, no evidence of chromosomal damage in nestlings was
found.” Based on only a few eggs, DDE in eggs from the Prime Hook National
Refuge were 0.6 ppm in 2002 compared to 5 ppm in 1974. Marginal reproduction
rates in the more polluted areas were the result of lost eggs. Lost eggs can be the
result of damaged or cracked eggs tossed out by the parents, eggs lost from precari-
ous nests (e.g., on fl oating buoys), human interference, or predation. Some of these
factors are more prevalent in the more polluted areas because they are also the more
urbanized and industrialized areas. The authors concluded that “…the latitudinal
trends seen in egg contaminant exposure are unlikely to result from contaminant
exposure on the wintering grounds.” This idea is somewhat contradicted by the wide
range of DDE levels in eggs from each area (overall range of 0.17-4.61 ppm). No fi sh
residues were reported.
The fi nal osprey breeding study to be reviewed is one currently underway in
Newport Bay. Newport Bay has historically seen osprey stopping briefl y during
migration. Ospreys prefer coniferous snags (e.g., dead fi r trees) for nesting to minimize
predation as well as to have a clear path for fl ying to and from the nest. The snag
must also be close to fi shing grounds so that a nesting pair has ample access to food
for themselves and their young. Despite excellent fi shing grounds, Newport Bay has
historically not had this type of tree for nesting ospreys. In 1993, a wooden platform
was affi xed to the top of a 50 ft pole on Shellmaker Island in an attempt to attract an
osprey pair to nest. Nothing happened for more than a decade. Sticks were added in
an attempt to start the nest building activity. A pair built a nest in 2005. Mating
resulted in two nonviable eggs. The next year, mating resulted in the successful
production of two fl edglings. Breeding has continued successfully each year by this
pair. Tagging of the fl edglings began in 2008. A female osprey, fl edged at Shellmaker
Island in 2008, returned to the area in 2010 with a mate and built a nest on a new
platform at the San Joaquin Wildlife Sanctuary (SJWS) in the lower drainage into
Newport Bay. This pair produced a single fl edgling in 2010. In 2011 the same pair
was in the process of raising two chicks, when suddenly both died of unknown
cause. Hemorrhaging was noted in their lungs. The adults appeared unharmed and
returned in 2012 to successfully fl edge two chicks. The reproductive data for the
two osprey pairs are listed in Table
22
below.
′
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