Environmental Engineering Reference
In-Depth Information
Table 20
The importance of wintering ground exposures to DDT in peregrine falcons in the late
1970s. Table 1 in Henny et al. (
1982a
) reproduced with permission
time the nests were unattended, leading to potentially greater predation by great
horned owls.
Considering the importance of the unknown exposure of ospreys to DDT in wintering
grounds, digression to an article by Henny et al. (
1982a
) is enlightening. Henny et al.
reported the measurement of DDT in the blood of peregrine falcons captured during
migration north in the spring and south in the fall (Table
20
). The peregrine falcon
migration is similar to that of the osprey.
The table requires explanation. HY falcons are those migrating in the year they
hatched. SY falcons are second year falcons and ASY means falcons migrating after
their second year. Focusing on the Texas data for female falcons, one can see that
just fl edged falcons on their way south have quite low levels of DDE. SY falcons
returning north in the spring of the next year have more than ten times as much
DDE in their plasma. Plasma levels are lower in SY falcons migrating south from
northern breeding areas. Apparently, body burdens gained in the south during the
winter are decreasing in the north during summer as a result of both egg laying and
ever decreasing exposures in the northern breeding areas. The same pattern would
be expected in osprey.
This exposure paradigm is even more important for the osprey since fl edglings
do not return to northern breeding grounds until their third year. Southern exposures
to DDT could explain the ever increasing bioconcentration factors calculated from
just northern exposures. As DDT levels decreased in the United States to levels
below those in Latin America, the importance of the unknown southern exposure
eventually becomes essential to understanding the relationship between DDE
residues in the fi sh diet and levels in eggs associated with thinning and hatching
failure. With the understanding gained from this digression, let us resume reviewing
the chronology of studies of the effects of DDE on osprey reproduction.
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