5. Conclusion
Our study indicates that bird-repellent rodenticide formulations
are a promising means of protecting non-target
birds from rodenticide applications. Although we observed
no mortalities among non-target birds, we observed only
10% and 30% mortality among target rodents offered
rodenticide baits treated with 1% and 2% anthraquinone,
respectively. Whereas black-tailed prairie dogs exhibited
some repellency for 0.5–4% anthraquinone during our
concentration–response experiment and anthraquinone
threshold concentrations have been recently estimated for
non-target birds (e.g., 0.145% anthraquinone for Canada
geese; Werner et al., 2009), we recommend additional
development and evaluation of anthraquinone-treated
rodenticide baits to reduce non-target consumption of
rodenticide baits by wild birds. Supplemental performance
testing and field efficacy studies are needed to evaluate
response of non-target birds and target rodents offered
baits treated with 0.25–0.5% anthraquinone and 2% zinc
phosphide (i.e., actual concentrations; wt/wt).