Proceedings of the Vertebrate Pest Conference

In an effort to reduce damage by house finches (Carpodacus mexicanus) to grapes, field trials were undertaken in two red winegrape (Pinot Noir and Pinot Chardonnay) vineyards in California using prebait (rape seed and canary grass seed) followed by baiting with these same seeds treated with a hydrochloric acid and 4-aminopyridine (Avitrol) solution. Seed was placed in V-shaped troughs placed 1-3 feet above the vines; treated seed was blended in a ratio of 2 untreated seeds to 1 treated seed, and 3 parts canary grass seed to 1 part rape seed. Prebait seed was replaced with treated seed when estimated maximum house finch visitation occurred, and was exposed from 1 to 4 days, with removal when house finch feeding from troughs ceased; the prebait and treatment schedule was then repeated as necessary until harvest. Bird counts were made throughout the trial, and winegrape damage assessment was conducted. In one test vineyard, early in the trial damage in the treated plot was assessed at 3% while damage in the control plot was insignificant, and house finches abandoned the test site. In the other test vineyard, the treatment plot received 7% damage while the two control plots received 17% and 13% damage, respectively. As a result of the treatment, grape damage was reduced approximately 50% as compared to bird damage the previous year. Data support the conclusion that Avitrol-affected house finches may stimulate an avoidance reaction among other flock members.