Wikipedia
A klopotec (pronounced ) is a wooden mechanical device on a high wooden pole, similar to a windmill. It is used as a bird scarer in the vineyards of traditional wine-growing landscapes of Slovenia, Austria, and Croatia. It is one of the symbols of Slovenia and Styria.
The windmill in the Slovene Hills typically has four blades, and in Haloze six blades, driving an axis with a sail or vane that is constructed to swivel so it is always positioned perpendicular to the wind. As the axis rotates, wooden hammers are lifted off their resting position by fixed notches. As they fall back, they rhythmically impact on a wooden board. While the quality of the sound is dependent on the wood of which the hammers and sounding boards are made of, the rattle frequency depends on the number of hammers, as well as changes in wind speed.
The device is used primarily to scare starlings and other birds off the vineyards so that they do not peck grapes. A folk belief also states that klopotecs drive snakes from the vineyards and soften grapes. In Catholic folk music of its region of origin, it is sometimes combined with an organ stop and used as a rural church instrument (e.g. in Gleisdorf parish church).