Ornithologists claim that this is the result of intensifying agricultural production (too early mowing, cutting of hedges and trees, intensive use of fertilisers), changing of lowland meadows into arable land, and overgrowing in other areas.
Ornitologi ugotavljajo, da je to povezano z intenzifikacijo kmetijske pridelave (prezgodnja košnja, krčenje mejic in dreves, intenzivno gnojenje), s spreminjanjem nižinskih travnikov v njive in z zaraščanjem v drugih predelih.