SYMPOSIA PAPER Published: 01 June 1979
STP34974S

Procedure for Visually Estimating Bird Damage to Grapes

Source

Bird damage was assessed in 48 plots of wine grapes located in two regions of California during 1977. In each plot, five randomly selected grape bunches on each of 40 randomly selected vines were visually assessed, using an eight-value rating scale based on the arc-sine transformation. A hoop sampler and a rope device aided random selection of the bunches in untrellised and trellised vineyards, respectively. The mean damage ratings, calculated for use in analysis of variance, were backtransformed to estimate the percentage loss in the plots. Independent observers using this system were reasonably accurate in estimating known levels of bird damage. Because of the relative variation among the plots between the among-vine and the within-vine variances, the optimum plot sampling rates for the number of vines and bunches per vine varied greatly. The procedure tested is probably most useful for comparing bird damage levels on experimental plots of grapes, but could be adapted for estimating percentage bird losses in vineyards.

Author Information

DeHaven, RW
U.S. Fish and Wildlife Service, Denver Wildlife Research Center Field Station, Davis, Calif
Hothem, RL
U.S. Fish and Wildlife Service, Denver Wildlife Research Center Field Station, Davis, Calif
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Details
Developed by Committee: E35
Pages: 198–204
DOI: 10.1520/STP34974S
ISBN-EB: 978-0-8031-4748-5
ISBN-13: 978-0-8031-0594-2