Repellency of methiocarb-treated grapes to three species of birds

Tests were conducted to evaluate the repellency of methiocarb-treated grapes to European starlings (Sturnus vulgaris), American robins (Turdus migratorius) and house finches (Carpodacus mexicanus). Birds were individually caged, and provided with grape bunches during a series of daily 5-h feeding trials, and repellency was determined by comparing damage done to the methiocarb-treated grapes with each bird's earlier damage to untreated grapes. A significant R₅₀ (the estimated concentration that repels 50% of the birds) of 7.3 g methiocarb per 1 water was found during the 1st day that starlings were exposed to treated grapes. However, during 4 subsequent days of exposure damage became quite variable while generally increasing to near pretreatment levels. During their 3rd day of exposure to methiocarb, a significant R₅₀ of 2.8 g/l was recorded for the robins, and repellency was more uniform during the course of the five treatment feeding trials than for either the starlings or finches. The most pronounced repellency was for the finches, which had significant R₅₀'s ranging from 0.3 to 0.9 g/l. The amount of damage caused by finches declined sharply between the 1st and 5th days of exposure to the repellent.