RAPTOR-MIMICKING KITES FOR REDUCING BIRD DAMAGE TO WINE GRAPES

Authors

Roger L. Hothem, Wildlife Biologists, U.S. Fish and Wildlife Service, Dixon Field Station, Denver Wildlife Research Center, 6924 Tremont Road, Dixon, California
Richard W. DeHaven, Wildlife Biologists, U.S. Fish and Wildlife Service, Dixon Field Station, Denver Wildlife Research Center, 6924 Tremont Road, Dixon, California

Date of this Version

February 1982

Document Type

Article

Abstract

Preliminary tests in California vineyards during 1979 and 1980 indicated that a raptor-mimicking kite suspended from a helium-filled balloon (kite-balloon or KB) could reduce bird damage to ripening wine grapes. Based on the results of both damage assessments and bird censuses, one KB per hectare, deployed for alternate 1-wk periods, reduced losses caused by birds by about 33% in 1979 and by an average of 48% in 1980 when compared with 1-wk control periods. Habituation by the birds to the KB appeared to reduce its effectiveness over time in 1979, but this problem was reduced in 1980 by regularly changing the KB components and deployment methods. Based on tests conducted in 1981, polyurethane tetroons (PTs) were the longest lasting of four balloons currently available for use in KBs, but in high winds they flew too close to the ground to keep kites aloft. Spherical balloons made of rubber had better flight characteristics but shorter longevity than the PTs. More testing is needed to evaluate the effectiveness of KBs for protecting entire vineyards during whole-season tests and to identify situations where their use may be cost-effective.