Mean p,p'-DDE (DDE) residues in plasma of combined adult and subadult
female peregrine falcons (Falco peregrinus) decreased significantly in
spring migrants captured at Padre Island, Texas, between 1978 and 197
9 (1.00 mu g/g wet wt), 1980 (0.57), 1984 (0.50), and 1994 (0.34). No
other organochlorine pesticides were detected (detection limit, 0.02 m
u g/g) in 1994. Mirex, oxychlordane, dieldrin, heptachlor epoxide, and
the parent material DDT were routinely found in plasma samples in ear
lier years. Polychlorinated biphenyls (PCBs) were found in 75% of the
adult females in 1994, but PCB data collected in 1984 were not compara
ble. The decrease in organochlorine pesticide residues was associated
with peregrine population increases in the Arctic and elsewhere in Nor
th America. The arctic peregrine (F. p. tundrius) was removed from the
list of Threatened and Endangered Species by the U.S. Fish and Wildli
fe Service in 1994. Satellite telemetry and plasma sampling provide ne
w insight into continuing sources of DDE and PCBs. Chemicals that repl
aced organochlorine pesticides require additional investigation in Nor
th and South America.