Individual study: Establishing songbird nest boxes increased avian insectivores and reduced herbivorous arthropods in a Californian vineyard, USA
Jedlicka J.A., Letourneau D.K. & Cornelisse T.M. (2014) Establishing songbird nest boxes increased avian insectivores and reduced herbivorous arthropods in a Californian vineyard, USA. Conservation Evidence, 11, 34-38
California winegrape growers interested in merging conservation with agricultural production have established nest boxes for songbirds in their vineyards. A common occupant, the native western bluebird Sialia mexicana consumes arthropods during the breeding season. We measured the effect of enhanced avian activity on arthropod pests and natural enemies by experimentally establishing songbird nest boxes in one section of a 50 ha vineyard. During avian brood production and shoot extension of the grapevines, we compared the composition of the arthropod community in the nest box area with that of a no-nest box control area. During peak nest box occupancy, the nest box area had significantly fewer herbivorous arthropods, including leafhopper pests, than the control area. There were also significantly fewer large, beneficial, predatory arthropods in the nest box treatment compared to the control area. After chicks hatched, small arthropods decreased in the nest box treatment area, while increasing in the control area. Therefore, although avian foraging near nest boxes reduced the abundance of beneficial arthropods, harmful herbivorous insects did not increase in the nest box treatment even when they increased in the control area. This indicates an overall positive effect of nest box provision on pest abundance in a large, commercial vineyard.