Abstract
Insectivorous Western Bluebirds (Sialia mexicana) occupy vineyard nest boxes established by California winegrape growers who want to encourage avian conservation. Experimentally, the provision of available nest sites serves as an alternative to exclosure methods for isolating the potential ecosystem services provided by foraging birds. We compared the abundance and species richness of avian foragers and removal rates of sentinel prey in treatments with songbird nest boxes and controls without nest boxes. The average species richness of avian insectivores increased by over 50 percent compared to controls. Insectivorous bird density nearly quadrupled, primarily due to a tenfold increase in Western Bluebird abundance. In contrast, there was no significant difference in the abundance of omnivorous or granivorous bird species some of which opportunistically forage on grapes. In a sentinel prey experiment, 2.4 times more live beet armyworms (Spodoptera exigua) were removed in the nest box treatment than in the control. As an estimate of the maximum foraging services provided by insectivorous birds, we found that larval removal rates measured immediately below occupied boxes averaged 3.5 times greater than in the control. Consequently the presence of Western Bluebirds in vineyard nest boxes strengthened ecosystem services to winegrape growers, illustrating a benefit of agroecological conservation practices. Predator addition and sentinel prey experiments lack some disadvantages of predator exclusion experiments and were robust methodologies for detecting ecosystem services.
Highlights
Ecosystem services such as pest control and pollination are functions provided by biological diversity that are critical to human societies and their agricultural production [1,2]
Nest box Occupancy In 2009, three avian species were the predominant occupants of vineyard nest boxes: Western Bluebirds (76.1% of box pairs), Tree Swallows, and Violet-green Swallows (Tachycineta bicolor and Tachycineta thalassina respectively, 17.4% of box pairs combined)
Providing songbird nest boxes in vineyards nearly quadrupled the abundance of insectivorous birds, most notably the Western Bluebird whose density increased tenfold
Summary
Ecosystem services such as pest control and pollination are functions provided by biological diversity that are critical to human societies and their agricultural production [1,2]. Bird-friendlyH coffee systems are well-known for their conservation value, in providing habitat for insectivorous migrant bird species [5,6]. Conservation of birds in agricultural landscapes may benefit growers through the provision of pest control services. Outside exclosures avian predation of insect pests increased quantities of marketable fruit and raised farmer income in apple [9,10] and coffee [11,12] production systems
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
