Insectivorous birds disrupt biological control of cereal aphids.
Insect-feeding birds may interfere with trophic interactions in plant-insect food webs, which may be particularly important in agroecosystems. Here, we studied how Eurasian Tree Sparrows (Passer montanus) affect aphids and their predators in cereal fields using bird exclusion experiments. The Tree Sparrows fed their nestlings with aphid antagonists. Hoverflies and ladybird beetles accounted for 77% of the food for the nestlings during peak aphid density. When birds were excluded, densities of hoverfly larvae, which were the most abundant aphid predator group in the cereals, were 4% higher in wheat and 45% higher in oat, while aphid densities were 24% lower in wheat and 26% lower in oat. The demonstrated disruption of biological control by mesopredators through bird predation may be a common phenomenon in cropping systems characterized by small-sized and abundant pest species. Management of biotic interactions such as biological control needs a broad food-web perspective, even in simplified agroecosystems.
Agroecology, University of Goettingen, Grisebachstraße 6, 37077, Göttingen, Germany.
Ingo
I
Grass
Agroecology, University of Goettingen, Grisebachstraße 6, 37077, Göttingen, Germany.
Katrin
K
Lehmann
Agroecology, University of Goettingen, Grisebachstraße 6, 37077, Göttingen, Germany.
Carsten
C
Thies
Agroecology, University of Goettingen, Grisebachstraße 6, 37077, Göttingen, Germany.|Centre of Biodiversity and Sustainable Land Use (CBL), University of Goettingen, Göttingen, Germany.
Teja
T
Tscharntke
D000818:Animals; D001042:Aphids / Q000502:physiology*; D001717:Birds / Q000502:physiology*; D001517:Coleoptera; D002523:Edible Grain; D005247:Feeding Behavior; D010572:Pest Control, Biological; D011235:Predatory Behavior

Passer montanus
; Sparrows; aphids; biological control; cascade effects; cereals; food webs; hoverflies; intraguild predation; ladybird beetles; mesopredators; trophic interactions