Avian Conservation Practices Strengthen Ecosystem Services in California Vineyards

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.

Vegetation connectivity increases ant activity and potential for ant‐provided biocontrol services in a tropical agroforest

“…Restricting movement of sentinel prey, either by gluing them to observation sites or by freezing them, is a common technique for assessing predator behavior (Armbrecht & Perfecto, ; De la Mora et al. ; Jedlicka, Greenberg, & Letourneau, ). We used frozen (dead) sentinel prey to increase the availability and similarity of beetles on cards and to reduce the potential for live prey to escape from the arena.…”

Natural cavity restoration as an alternative to nest box supplementation

“…Not surprisingly, nest‐site supplementation by addition of nest boxes has become an increasingly common restoration strategy in modified landscapes, mainly in forested areas (Franzreb ; Harper et al ; Goldingay et al ; Le Roux et al ). Nest box supplementation has been reported to have economic, sociological, and scientific benefits (Møller ; Jedlicka et al ) as well as population increases of threatened species (e.g. Václav et al ; Berthier et al ; Kiss et al ).…”

Multiscale habitat mediates pest reduction by birds in an intensive agricultural region

“…In more intensive agricultural landscapes, increases in pest reduction by birds were attributed to nest box additions (Jedlicka et al. ), proximity to woody field margins (Garfinkel and Johnson ), or habitat‐linked increases in bird abundance (Kross et al. ).…”