Bird damage to wine grapes was surveyed in nine counties in the coastal area of central California in 1973. Damage to 90 bunches of grapes in each of 140 randomly selected plantings was visually estimated according to seven damage classes. Results indicated that birds damaged or destroyed 1.99%± 1.08% (95% confidence interval) of the crop, or about 1,547 to 5,219 tons of grapes worth more than $0.75 million. Napa, San Benito, and Sonoma Counties had the highest dollar losses. Upper bunches on grapevines were more heavily damaged than lower ones, and dark-colored varieties were more heavily damaged than light-colored ones. Early-maturing and late-maturing varieties were not differentially damaged. Of the birds observed in the sampled plantings, 51.5% were house finches (Carpodacus mexicanus) and 25.8% were starlings (Sturnus vulgaris); 16 other species made up the remaining 22.7%. Modifications of the survey methods are suggested for similar surveys of bird damage to grapes and for surveys where higher accuracy is desired.

Bird damage appraisal methods that have been developed and published are reviewed. For sprouting field crops, they exist for corn and for rice. For mature field crops, published appraisal methods are available for corn, peanuts, and rice. For fruit crops, appraisal methods are cited for cherries (control evaluation; and extensive survey) and for blueberries.

Damage caused by birds to ripening sunflower was evaluated in 60 fields (about 70% of all planted fields) in the Sacramento Valley, California, during 1980 and 1981. Overall monetary losses were roughly $6,800 (24 fields) and $7,400 (36 fields) in 1980 and 1981, respectively. The percentage losses estimated for the individual fields were low, ranging from O to 5.4% of the crop; in about two-thirds of the fields, losses were <0.5%. For the 12 fields with the highest (≥1 .0%) damage, the average per acre monetary loss was roughly $18. Damage levels within local areas were relatively constant between the two years. Although several species of birds caused damage, house finches (Carpodacus mexicanus) were apparently most important. Their foraging behavior differed from that of blackbirds, which fed extensively on insects in addition to sunflower. The presence of large numbers of blackbirds or finches in fields was not always an indication of bird damage. Additional research may lead to recommendations for alleviating the moderate losses which a few growers now incur.

Studies by the U. S. Fish and Wildlife Service of the efficacy of methiocarb for reducing bird damage to sprouting corn, rice, soybeans, lettuce, and sugar beets, and to ripening rice, grain sorghum, wheat, cherries, grapes, and blueberries have shown it to be an effective, broad-spectrum bird repellent and crop protectant. The short-term plans of the Service for the further development and testing of methiocarb are reviewed. Also discussed is some of the rationale behind the use of chemical repellents to prevent agricultural damage by birds.

Bird damage was assessed weekly from soon after anthesis until harvest in two sunflower fields in the Sacramento Valley, California, during 1982. Damage chronology was similar at both sites, with damage concentrated in the second to fourth weeks after anthesis when the seeds were in the doughy stage of development. Less than 10% of the total losses caused by birds occurred during the final month before harvest. Overall bird damage was quite low (0.20 and 0.26%) in each field and in one, damage by wind was 2.4 times greater than that caused by birds. Brewer's blackbirds (Euphagus cyanocephalus) and house finches (Carpodacus mexicanus) both occurred in low-to-moderate numbers in one field, while high numbers of blackbirds, mostly red-winged blackbirds (Agelaius phoeniceus) occurred at the other field. At both fields, the numbers of blackbirds recorded peaked during the dough stage of sunflower development, whereas finches were most numerous somewhat later in the damage season. Analysis of the esophagi of 15 red-winged blackbirds collected at one field showed that in addition to sunflowers, various wild grass seeds and insects were consumed.

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.