DOI: 10.5061/dryad.z34tmpg8t
title: Birds suppress pests in corn but release them in soybean crops within a mixed prairie/agriculture system

description: Birds provide ecosystem services (pest control) in many agroecosystems and
 have neutral or negative ecological effects (disservices) in others.
 Large-scale, conventional row crop agriculture is extremely widespread
 globally, yet few studies of bird effects take place in these
 agroecosystems. We studied indirect effects of insectivorous birds on corn
 and soybean crops in fields adjacent to a prairie in Illinois (USA). We
 hypothesized that prairie birds would forage for arthropods in adjacent
 crop fields and that the magnitude of services or disservices would
 decrease with distance from the prairie. We used bird-excluding cages over
 crops to examine the net effect of birds on corn and soybean grain yield.
 We also conducted DNA metabarcoding to identify arthropod prey in fecal
 samples from captured birds. Our exclosure experiments revealed that birds
 provided net services in corn and net disservices in soybeans. Distance
 from prairie was not a significant predictor of exclosure treatment effect
 in either crop. Many bird fecal samples contained DNA from both beneficial
 arthropods and known economically-significant pests of corn, but few
 economically-significant pests of soybeans. Song Sparrows (Melospiza
 melodia), one of our most captured species, most commonly consumed corn
 rootworms, an economically-significant pest of corn crops. We estimated
 that birds in this system provided a service worth approximately US
 $275/ha in corn yield gain, and a disservice valued at approximately
 $348/ha in soybean yield loss. Our study is the first to demonstrate that
 birds can provide substantial and economically valuable services in field
 corn, and disservices in soybean crops. The contrasting findings in the
 two crop systems suggest a range of bird impacts within widespread
 agro-ecosystems and demonstrate the importance of quantifying net trophic
 effects.
description: Exclosure data presented are indices of corn and soybean crop
 yield from control and bird-exclosure plots in northern Illinois, USA,
 2016. Measurements were taken for five plants within each plot. Exclosures
 were in place for approximately 3.5 months before the crops in exclosures
 and controls were harvested by hand and measurements taken.
 Molecular data includes raw read counts of arthropod OTUs as
 rows, and bird fecal samples as columns. Each row is an OTU, and the
 assigned taxonomy is included in the first column. Data have not been
 normalized by total read counts per sample.  
description: <strong>For exclosure data:</strong>Variables for
 corn include "ID" (letter from A-F indicating plot);
 "distance" (close is 5m from field edge, far is 55m from field
 edge); "num.kernals" (count of corn kernals on the primary
 ear); "all_kernals" (total number of corn kernals per plant from
 both primary and any secondary ears); "primary_dry_mass" (dry
 mass of all kernals removed from cob from primary ear only);
 "all_dry_mass" (combined dry mass of all kernals removed from
 cob from all ears per plant); "ave_kernal"
 (all_dry_mass/all_kernals).  Variables for soybeans
 include "ID" (letter from A-F indicating plot);
 "distance" (close is 5m from field edge, far is 55m from field
 edge); "count_pods" (number of soybean pods per plant);
 "count_beans" (number of soybeans per plant, counted after
 removing from pods); "dry_mass" (total dry mass of all soybeans
 per plant); "wet_mass" (mass of soybeans per plant measured upon
 harvest but before being oven dried); "ave_bean"
 (dry_mass/count_beans) <strong>For DNA
 data: </strong>Only OTUs assigned to phylum Arthropoda are included
 here. Because these data include read counts per OTU by sample, we have
 included species here that did not pass our minimum read count to be
 included in further analyses. We also included samples here that were
 later thrown out due to poor data quality.