Certain bird species such as the thrush (blackbird), pheasant, partridge, sparrow and starling are attracted to the sweet grapes during the ripening period from August or the grape harvest and can cause a considerable reduction in yield. Bird plagues in the vineyards have been described in ancient times and are still a worldwide problem today. In spring and summer, however, they can be very desirable as insectivores and thus as beneficial insects. In extreme cases very large flocks of up to 10,000 birds and more can occur, this is especially true for the starling. If such a flock of birds settles on a vineyard, it is "harvested" in a short time. As a negative side effect, damaged or pecked berries promote the penetration of microorganisms such as bacteria and fungi and thus the occurrence of grape rot.
Various measures are taken to prevent this or limit the damage. The former use of avicides (pesticides) is now severely restricted or even prohibited. As a substitute, "aversive agents" (repulsives, repellents) are used, which are perceived through the sense of smell, but do not kill. This also includes physical methods. A relatively complex form is the spanning of the vineyards with nets. Here, care must be taken to ensure that the nets are visible to the birds so that they do not fly against them and injure themselves.
Often, however, these are optical devices such as scarecrows, acoustic wind-driven, noise-generating devices such as the Klapotetz, tapes with bird death cries or rifle shots, airplanes or personal surveillance by a vineyard keeper. The aim is to spread the birds over all the vineyards of a larger area as far as possible, thus minimising the damage to all the winegrowers. This is used in the context of biological or integrated plant protection.