Klopotec, a wooden mechanical device that makes a rattling sound in wind, has been a familiar sight in vineyards in parts of Slovenia for centuries. Meant to scare birds away from ripening grapes, nowadays these rattles invite people to come together and call for a good harvest.

One of the symbols of Slovenian viticulture, the klopotec or rattle is placed on a high pole above a vineyard and resembles a windmill. As the axis rotates in the wind, wooden hammers are lifted off their resting position by fixed notches. As they fall back, they rhythmically impact on a wooden board, making a sound.

Drago Korade, an amateur ethnologist who has written a book on these devices, estimates that klopotecs probably began to be erected in Slovenian lands in the first half of the 18th century. The oldest known depictions date back to the first half of the 19th century, of klopotecs at Bizeljsko Castle and at the estate of Archduke John at Meranovo near Maribor, he told the Slovenian Press Agency.

The klopotec is considered to be a Slovenian invention, but it is likely to have made use of certain technical solutions from German lands, where wind wheels are thought to have been used in vineyards and orchards. They were first placed in grain fields, but later became a permanent fixture in vineyards.

Oskar Neuvirt, the owner of a collection of klopotecs in Malečnik near Maribor, says there are three types of rattles. The Prlekija and Slovenske Gorice use one with four arms, the Haloze type has six arms and the Austrian one has eight. There are also dumb rattles, which have no hammers and are meant to chase away pests only by means of vibrations.

The devices come in different sizes and are made of different types of wood and in natural colours. The largest, which was entered in the Guinness Book of World Records in 2014, had 20.58 metres-long fan blades and was made by Stanko Habjanič in Hermanci in Miklavž near Ormož in the northeast of the country.

They are most widespread in the northeastern parts of the country. "They were erected in Slovenske Gorice, Prlekija and Haloze, and later spread to other wine-growing areas of Slovenia, and partly to the Zagorje region in Croatia, and in the north to the border areas of Hungary and Austria," Korade explained.

The devices are erected when the grapes start ripening, from 25 July to 15 August, and must be put away by 11 November at the latest. "A farmer who does not put away their rattles by St Martin's Day is thought to be lazy," said Neuvirt.

As birds got used to its rattling sound, the efficiency of klopotec is questionable. Nevertheless, many vine-growers keep putting them up as a way to preserve the tradition.

"The rattle used to scare away, but today it unites. It serves as an invitation to events, it heralds autumn, and when it is put up, everyone wishes for a good harvest. Unfortunately, some people also complain about the sound," said Neuvirt. "But this is our technical cultural heritage and it is right to nurture it," he added.

There are many customs and traditions associated with the klopotec. "The winemakers erect them to invite their friends and all those who have worked in their vineyard throughout the year. This is a way of saying thank you to them with a pleasant gathering, and of expressing the expectation of a bountiful harvest," Korade explained.