The western burrowing owl, Athene cunicularia hypugaea, is a Federal Species
of Concern, whose numbers and range have been drastically reduced from historic levels
in Texas. Burrowing owls roost and forage in agricultural areas, and it has been
hypothesized that exposure to insecticides may be a factor in the decline of their
population. Burrowing owls wintering in southern Texas use agricultural culverts in
cotton fields as roost sites, which may increase their risk of exposure to agricultural
chemicals, either through ingestion of contaminated prey or through dermal exposure to
agricultural runoff.
Simulation modeling was used to characterize the risks to individual burrowing
owls wintering in agricultural landscapes in southern Texas due to effects of exposure to
insecticides or other agricultural chemicals. The simulation model was created using
Stella® VII software (High Performance Systems, Inc., New Hampshire, USA). The
model is broken into four submodels simulating (1) foraging behavior of burrowing owls, (2) chemical applications to crops, (3) chemical transfer and fate in the crop soil
and prey items, and (4) chemical exposure in the burrowing owl.
This model was used to evaluate (1) which components of the model most affect
the endpoints, (2) the relationship between increased concentrations of agricultural
chemicals in culverts and subsequent lethal and sublethal effects from dermal exposure
to agricultural runoff, and (3) which agricultural chemicals have the greatest potential to
cause adverse effects in burrowing owls. Model results suggested (1) the half-lives of
agricultural chemicals in birds caused the most variation in the results, and data gaps
exist for several important model components (2), exposure to increased concentrations
of agricultural chemicals in culverts is unlikely to result in lethal effects, but is likely to
lead to sublethal effects in burrowing owls, and (3) the chemicals with the greatest
potential to negatively affect burrowing owls wintering in southern Texas are the OP
insecticides chlorpyrifos, dicrotophos, and disulfoton, the oxadiazine insecticide
indoxacarb, the herbicide trifluralin, and the defoliants tribufos and paraquat. The results
of this model demonstrate the usefulness of simulation modeling to guide future research
related to the conservation of burrowing owls.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/85982 |
| Date | 10 October 2008 |
| Creators | Engelman, Catherine Allegra |
| Contributors | Grant, William E., Mora, Miguel A. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | electronic, born digital |
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