Tillage systems and crop management have been proven to drastically change the soil ecosystem and hence change the foraging potential of agricultural fields for bird species. The size of the effect was investigated through transect counts of Eurasian Skylarks Alauda arvensis and collection of arthropods by ground search in conservation agriculture (CA) and conventional tilled (CT) spring barley fields located in Central Jutland, Denmark, in four fields of each type between 30 June and 24 July 2019. A mean of five times the number of birds and slightly less than two and a half times the weight of arthropods was found in CA fields compared to CT fields.The species diversity of arthropods tended to be higher in CA fields, with arachnids and Lepidoptera/Tenthredinidae larvae significantly more abundant. Using the daily energy requirements of a pair of Skylarks and their brood, the average daily foraging area that a breeding pair must search to satisfy the daily energy demand for themselves and their brood was estimated to be 587 m~2 in CA fields compared to 1337 m~2 in CT fields. Besides the five times higher density of Skylarks, the results suggest that spring barley fields grown according to CA rules provide enough food for a second brood, which does not seem to be the case in CT fields.
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