Proceedings of the Vertebrate Pest Conference

Field trials using methyl anthranilate, formulated as Bird Shield® repellent, were performed by aerial applicators at one pint per acre on sweet com in Colorado, and sunflowers in North Dakota, and at one, two, and four pints per acre on cherries in Washington. Nineteen com fields ranging in size from 9 to 25 acres were treated twice, at five day intervals, prior to harvest and compared with six untreated fields during a two year study. During the same time period ten sunflower fields, along with their adjacent cattail marshes were treated twice, at seven day intervals when the birds began to feed on the ripening seed, and compared with six untreated counterparts. Five out of the six untreated com fields were unharvestable, with greater than 75% damage, because of the severe damage caused by the resident populations of red-wing blackbirds (Agelaius phoeniceaus). Nine of the treated fields sustained no damage at all. The damage in the remainder was contained at pre-treatment levels (4% to 20%). The two applications of the repellent were sufficient to move the resident population of blackbirds out of the sunflower fields with no substantial damage to the crop. Untreated sunflowers sustained 783 to 90% damage. Treated sunflowers sustained between 2.6% to 3.4% damage. The difference in seed weights between untreated and treated plots was significant (P=0.01) with a mean weight of 0.018 g/cm2 of seed per head within the former and 0.084 g/cm2 of seed per head within the latter. Harvest weights ranged from 133 to 700 lbs/ac (mean=344) in the untreated plots while weights ranged from 1430 to 1909 lbs/ac (mean=1675) in the treated plots. No adverse effects were noted with fish or resident populations of ducks. The application of the repellent by helicopter reduced bird damage from just under 13% in one untreated cherry orchard to between 0.08% and 1.0% seven days later with 1, 2, and 4 pints/ac rates in comparable orchards. Greater differences were encountered when the repellent was applied at two additional sites. When 2 pints/ac was applied, bird damage was limited to 8% after 15 days when the untreated block sustained between 58% to 68% damage.