DOI: 10.25338/b8tk62
title: Data from: Shifts in species interactions and farming contexts mediate net effects of birds in agroecosystems

description: Some birds are viewed as pests and vectors of foodborne pathogens in
 farmlands, yet birds also benefit growers by consuming pests. While many
 growers seek to prevent birds from accessing their farms, few studies have
 attempted to quantify the net effects of bird services and disservices,
 let alone how net effects shift across farm management strategies. We
 quantified the net effect of birds on crop production across 20 California
 strawberry (Fragaria x ananassa) farms that varied in local management
 practices and landscape context. We surveyed farms for berry damage and
 bird droppings (as potential sources of pathogens), and implemented a
 large‐scale exclusion experiment to quantify the impact of birds on
 production. We found that birds had only a slightly negative overall
 impact on strawberry production, reducing economic value by 3.6%. Direct
 bird damage and intraguild predation contributed equally to this net
 effect, underscoring the importance of indirect trophic interactions that
 may be less apparent to growers. In simple landscapes (e.g., low
 proportions of surrounding seminatural habitat), birds provided pest
 control in the interiors of farm fields, and costs from bird damage to
 crops peaked at field edges. In complex landscapes (e.g., high proportions
 of seminatural habitat), birds were more likely to disrupt pest control by
 feeding as intraguild predators. Nonetheless, seminatural habitat dampened
 bird services and disservices, and our models predicted that removing
 habitat around farm fields would increase costs from bird damage to crops
 by up to 76%. Fecal contamination of crops was extremely rare (0.01%).
 However, both fecal contamination and bird damage did increase on farms
 with higher densities of fencing and wires, where birds often perch. Our
 results demonstrate that maintaining seminatural habitat around farms may
 enhance bird diversity and mitigate bird damage without increasing
 food‐safety risks. We also show that the net effects of birds depend on
 farming context and vary in complex ways in relation to locations within a
 farm, local farm attributes, and the surrounding landscape. This
 context‐specific variation must be considered in order to optimize the
 management of wild birds in agroecosystems.
description: Bird exclosure experiment and berry damage and fecal transect
 surveys on California strawberry farms. This dataset contains information
 on 1) berry damage and invertebrate sampling from a bird exclosure
 experiment (N=15), and 2) berry damage and bird fecal contamination from
 transect surveys (N=20) on organic strawberry farms in the California
 Central Coast in 2018. We excluded birds from strawberry plants with
 mesh-net cages and compared berry damage and insect communities between
 exclosure (no birds) and control (bird accessible) plots. We erected three
 paired exclosure and control plots on each farm for one month each during
 the spring (April-May, when strawberry yields were low) and summer
 (June-July, during peak strawberry production). Each week, we harvested
 berries from treatment plots and scored all ripe berries for damage. At
 the beginning and end of each round of the exclosure experiment, we
 vacuum-sampled invertebrates from eight plants within each plot. We
 surveyed berry damage and bird fecal contamination along three parallel,
 20m transects in strawberry rows on each farm. Berry damage surveys were
 limited to 20 plants per transect, sampling every 5 plants. We located
 exclosures and transects at the farm edge with the most seminatural
 habitat, as far from a farm edge as a possible, and halfway in
 between.
description: Each csv file has an accompanying txt file defining the column
 headings. All ripe berries were harvested
 from exclosure and control treatment plots at the beginning of each round
 of the exclosure experiment. Initial berry harvests during exclosure
 set-up are not included in this dataset. One paired
 exclosure treatment plot was removed from all exclosure analyses: Farm12,
 exclosure pair 1, early season – shading from vegetation made treatment
 plots not comparable Two
 additional paired exclosure treatment plots were removed from all
 exclosure berry damage analyses: Farm17,
 exclosure pair 3, late season- berries from control plots harvested by
 farmworkers Farm18, exclosure pair 1, late season-
 berries from control plots harvested by farmworkers