 |
| Columbia Environmental Research Center |
Brazos
Field Research Station Research Program
Environmental
Contaminants in Insectivorous Birds and Bats, Potential Prey of the Peregrine
Falcon in Big Bend National Park
Peregrine
falcons (Falco peregrinus) are recorded nesting in Big Bend National
Park, Texas, USA, and other areas of the Chihuahuan Desert since the early
1900s. From 1993 to 1996, peregrine falcon productivity rates were very low and
coincided with periods of low rainfall. However, low productivity also was
suspected to be caused by environmental contaminants. To evaluate potential
impacts of contaminants on peregrine falcon populations, likely avian and bat
prey species were collected during the 1997 breeding season in Big Bend National
Park. Overall, mean concentrations of DDE
[1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene], a metabolite of DDT
[1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane], were low in all prey species
except for northern rough-winged swallows (Stelgidopteryx serripennis,
mean=5.1 mg/g ww). Concentrations of mercury and selenium were elevated in some
species, up to 2.5 mg/g dw, and 15 mg/g dw, respectively, which upon consumption
could seriously affect reproduction of top predators. Based on data from this
study it was concluded that mercury, selenium, and DDE to some extent, may be
contributing to low reproductive rates of peregrine falcons in the Big Bend
region. (Environmental
Pollution, In Press)
To
further assess if reproductive failures in peregrine falcons nesting in Big Bend
National Park are linked to contaminant burdens in their prey, we proposed to
sample additional areas where peregrine falcons nest in Big Bend National Park,
and in a few selected sites of the protected areas Caņon de Santa Elena, and
Maderas del Carmen in Mexico. The objectives of this study were to determine
levels of selected inorganic and organic contaminants in potential prey (birds
and bats) of the peregrine falcon in the Canon de Santa Elena and Maderas del
Carmen protected areas in Mexico, and in Big Bend National Park, Texas. Work in
Mexico is pending.
During
the summer 2001, cliff swallows, northern rough-winged swallows, mourning doves,
and other passerine birds were collected again in Mariscal Canyon, Big Bend
National Park. Data from this second year will be helpful in providing
additional documentation on the potential effects of mercury and selenium on
reproduction of the Peregrine Falcon. Collaborators in this project include
biologists from Big Bend National Park and Texas Parks and Wildlife
Department.
