Engelman, Catherine Allegra (2008-05). Ecotoxicological simulation modeling: effects of agricultural chemical exposure on wintering burrowing owls. Master's Thesis. Thesis uri icon


  • 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(R) 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.

publication date

  • May 2008