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

Abstract

Habitat augmentation on farms is predicted to conserve biological diversity and support beneficial animals that reduce crop pests. Effectiveness of local habitat enhancement and subsequent pest reduction services can be mediated by the amount of habitat at larger scales. We tested whether the presence and increase of local and landscape scale bird habitat increased avian predator abundance and pest reduction by birds. We surveyed birds and performed a sentinel prey exclosure experiment in walnut orchards in the Sacramento Valley, California, USA—comparing predation probability between orchards with (n = 10) and without (n = 10) woody habitat in uncultivated orchard margins. We digitized seminatural habitat cover in landscapes around orchards to test the effectiveness of avian predators in reducing sentinel prey along a seminatural cover gradient of 0–38%. Experimental prey were diapausing larvae of Cydia pomonella (L.) (Lepidoptera: Tortricidae; codling moth), a significant pest of walnuts, which overwinter in cocoons in orchards, emerge as adults, and produce larvae that feed on the nuts the following spring. Permitting bird access to cocoons increased larval predation from 11% (caged) to 46% (no cage), and predation increased with increasing proportions of seminatural habitat within 500‐m of orchard transects. Predation also increased as the size and bark furrow depth of walnut trees increased, likely because these characteristics were associated with increasing abundance of avian predators with functional traits specific to consuming tree‐dwelling cocoons (e.g., woodpeckers). The presence and increasing complexity of local margin habitat increased the species richness and abundance of avian predators but was not predictive of cocoon predation. Consistent with intermediate landscape‐complexity hypothesis predictions, the effect size of woodpecker abundance on predation was large in simple landscapes (1–20% seminatural cover) and low in complex landscapes (>20% cover). Contrary to predictions, effect size was large in cleared landscapes (<1% cover), suggesting that orchards supported predators in cleared landscapes, with positive effects on pest reduction. We provide evidence that increasing the abundance of avian predators with traits specific for consuming target pests—by retaining old trees and seminatural cover—can increase orchard pest reduction services in an intensive agricultural region.

Ant and termite diversity in Indonesian oil palm plantation: Investigating the effect of natural habitat existence

“…insectivorous birds and ants) that can affect the diversity of termites. Research by Heath and Long (2019) revealed that the predation of insectivorous birds increased with an increasing area of semi-natural habitat in orchards. This is related to the needs of insectivorous birds to consume a lot of insects (Nyffeler et al 2018).…”

Combining DNA metabarcoding and ecological networks to inform conservation biocontrol by small vertebrate predators

“…2016, Kaiser‐Bunbury et al. 2017, Heath and Long 2019). The management of multifunctional landscapes should therefore target at benefiting service‐providing organisms to enhance the flow, stability and resilience of ecosystem services supporting production (Doré et al.…”

“…Landscapes providing multiple products and services (i.e., multifunctional) are key to combine food security and biodiversity conservation worldwide, as they integrate human activities with the preservation of ecosystem structure and function Merenlender 2018, Manning et al 2018). In such landscapes, biodiversity contributes to food and fiber production, and to reduce its negative environmental externalities, by providing critical services such as pollination and pest control (Mace et al 2012, Maas et al 2016, Kaiser-Bunbury et al 2017, Heath and Long 2019. The management of multifunctional landscapes should therefore target at benefiting service-providing organisms to enhance the flow, stability and resilience of ecosystem services supporting production (Dor e et al 2011, Bommarco et al 2013, Tittonell 2014).…”

Ecological intensification and diversification approaches to maintain biodiversity, ecosystem services and food production in a changing world

“…In sunflower fields, hedgerows reduced damage to sunflower seeds from sunflower moths below the economic threshold for pesticide use without increasing damage due to pest birds [ 33 ]. However, in walnut orchards, hedgerows increased bird predator without control of codling moth, probably because walnut orchards themselves supported the presence of the two woodpecker species that controlled the moth [ 38 ]. Similarly for pollination services, hedgerows increased seed set provided by native bees for potted canola in a sentinel experiment, but had no effect on sunflower seed set at the field scale [ 39 , 40 ].…”