Ma. Mora et al., POTENTIAL EFFECTS OF ENVIRONMENTAL CONTAMINANTS ON RECOVERY OF THE APLOMADO FALCON IN SOUTH TEXAS, The Journal of wildlife management, 61(4), 1997, pp. 1288-1296
Efforts to reintroduce the aplomado falcon (Falco femoralis) into its
former range in the southern part of Texas began in 1977. Not until 19
93, however, were a significant number (26) of fledgling aplomado flac
ons released. The first nesting pair of aplomado falcons was reported
near the Brownsville Ship Channel during 1995. Because of a long histo
ry of pesticide use in the Lower Rio Grande Valley, during 1993-94 we
investigated the accumulation of environmental contaminants in plasma
of aplomado falcons released at the Laguna Atascosa National Wildlife
Refuge. We also assessed the potential contribution of typical prey sp
ecies to aplomado falcon contaminant burdens. Organochlorine pesticide
s and PCBs were below detection limits (wet wt basis) in plasma; howev
er, some organochlorines including 1.75 and 1.41 mu g/g p,p'-DDE, and
0.49 and 1.52 mu g/g total PCBs were detected in addled eggs collected
in 1995 and 1996. Mercury also was detected at 1.5 and 4.1 mu g/g dry
weight in the addled eggs collected in 1995 and 1996. We detected DDE
(range 0.02-0.25 mu g/g) in carcasses of potential prey of the aploma
do falcon. Trace metals also were detected in potential prey at levels
which are not of concern, except for Hg, which was high in a few mead
owlarks. Low levels of DDE and most trace metals in potential prey, in
cluding mourning doves (Zenaida macroura) and eastern meadowlarks (Stu
rnella magna), are not likely to result in adverse effects on the aplo
mado falcon in the Lower Rio Grande Valley. However, elevated Hg resid
ues in meadowlarks (in a few cases) and potentially higher DDE levels
in other prey species such as the great-tailed grackle. (Quiscalus mex
icanus) could result in negative effects on reproduction and survival
of some aplomado falcons in south Texas.