FEEDING DETERRENCE OF ANTHRAQUINONE, ANTHRACENE, AND ANTHRONE TO RICE-EATING BIRDS

Safe, effective bird repellents are needed as seed treatments and for many other agricultural uses. Quinones are distributed widely in natur e and many have predator defense and antiherbivory functions. One comp ound, 9,10-anthraquinone, was identified as a bird repellent in the 19 40s, but is not registered for use in the United States. We evaluated it and 2 structurally related compounds, anthrone and anthracene, for repellency to rice-eating birds. In choice tests with individually cag ed red-winged blackbirds (Agelaius phoeniceus) anthraquinone and anthr one produced comparable reductions in consumption of treated rice at r ates of 0.05, 0.10, and 0.25% (g/g). At 0.50%, however, only anthraqui none suppressed consumption of untreated rice as well as treated rice. Anthracene was least effective of the 3 compounds and was tested only at 0.50%. In 1-cup tests, consumption of anthraquinone-treated rice b y individual blackbirds was suppressed at 0.10, 0.25, and 0.50%. Rice consumption by individually caged female boat-tailed grackles (Quiscal us major) exposed to the 0.50% treatment was similar to that of redwin gs at the 0.10% treatment. In choice tests of 3-bird groups in large f light enclosures, red-winged blackbirds discriminated strongly against 0.25% anthraqunione-treated rice. Observations of videotaped birds re vealed no evidence of contact irritation or unpleasant taste; rather p ost-ingestive illness, as evidenced by one vomiting bird, suggests tha t anthraquinone repellency is due to learned behavior.