Can hay harvesting detrimentally affect adult butterfly abundance?

Butterfly transects were carried out in the meadows and tracks of a 1.5 × 1.6 km study area in the Cantabrian section of the Picos de Europa, Spain to examine the impact of hay harvesting on adult butterfly numbers. Overall butterfly numbers significantly decreased between transect counts taken before and after harvesting in cut fields; no such decline was evident in fields without active management (harvesting/grazing) over the same period. Family-level analysis showed hay harvesting to significantly impact on the Satyridae but not other groups. In fields not undergoing active management no Family-level declines were evident, but the Lycaenidae significantly increased in abundance over the same period. Butterfly abundance on tracks surrounding the meadows significantly decreased during the hay harvest period, but this was not reflected in significant decreases in any particular Family group. The results are discussed in relation to the time of harvesting during the day, and socioeconomic changes in extensive pastoral landscapes.