Environmental Engineering Reference
In-Depth Information
The fi rst report of a signifi cant recovery of ospreys was by Spitzer et al. in 1978 ,
6 years after the ban of DDT. Eggs collected from osprey populations in
Connecticut and eastern Long Island from 1967 to 1970 had 15-20% thinning,
approximating the critical level associated with hatching failure in other species.
DDE levels in osprey eggs from this area declined fi vefold between 1969 and
1976 and threefold between 1973 and 1976. “The productivity of these ospreys has
since increased from about 0.5 fl edged young per pair in 1969-1973 to 1.2 fl edged
young in 1976-1977 (Fig. 1), approaching the range observed in 1938-1942.”
The results are reproduced in Fig. 7 .
Productivity improved when DDE residues in eggs fell below 12 ppm (60 ppm
dry weight), a fi nding that is consistent with those of Henny et al. ( 1977 ) for other
areas. The authors acknowledged that dieldrin probably affected survival and
reproduction of ospreys in the Connecticut River estuary. No fi sh residue data were
reported.
MacCarter and MacCarter ( 1979 ) reported improving reproduction in osprey at
Flathead Lake in Montana even with high egg residues of DDTs, reproduced in
Table 14 .
From 1967 to 1977, the number of breeding adults gradually increased even
though productivity was marginal as might be expected with the high levels of
DDTs. Eggshell thinning and fi sh residues were not reported. The productivity data
are reproduced in Table 15 .
A report by Spitzer et al. in 1983 gave further indication of the recovery of osprey
breeding along the northeastern coast as shown in Fig. 8 .
The authors noted that DDE in osprey eggs had not been measured since 1976.
Presumably DDE residues were declining as reproduction improved. They also made
note of a brood-size reduction of 50% or more due to food limitations on Gardiner
Island, the same island mentioned as impacted by DDT in the NAS recommendation
for marine fi sh.
Spitzer and Poole ( 1980 ) and Poole ( 1989 ) revisited the issue of the struggling
population of ospreys on Gardiner Island. The population was decimated by DDT
in the 1950s and 1960s. Local citizens took up the cause to save the osprey. They
sued Suffolk County to stop spraying DDT for mosquito control and achieved a ban
on eastern Long Island. This local citizens group later became the Environmental
Defense Fund. One of their members, Dennis Puleston, was an author of the 1978
report (Spitzer et al.) on the recovery of osprey populations on eastern Long Island.
Recovery of the osprey on Gardiner Island was well underway in the 1970s when
reproduction failed again due to a limited food supply. Apparently male osprey had
to travel long distances to reliable supplies of fi sh in the marshes of the south fork
of Long Island. According to the authors, when this colony thrived it was dependent
on menhaden in nearby Gardiner's Bay. Excessive commercial fi shing removed this
food source, leading to a marginal food supply.
Reporting on a national survey of osprey breeding in 1983 , Henny stated:
“Ospreys at locations with poor production have all showed improvement following
the DDT ban in 1972.”
Wiemeyer et al. ( 1988 ) reported DDT effects on osprey eggs and reproduction
from several data sets generated in the 1960s and 1970s. Some declines in residue
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