Wild birds can be serious pests on farms by damaging produce and introducing food safety hazards to production fields and packinghouses. The most serious crop damage is usually caused by fruit- or seed-eating species such as blackbirds, cardinals, robins, or crows, whereas other species such as sparrows, finches, and starlings can take up residence in farm buildings and quickly become a nuisance. Creating an effective management plan to deter wild birds from fields and buildings begins with correctly identifying bird species and the damage that they are likely to cause. Just as different kinds of pest insects target different plants at different times of the year, not all birds feed in the same way, nor at the same time. Targeting deterrence strategies toward specific species is more cost-effective than a “catch-all” approach and reduces the likelihood that nontarget species are affected. The most effective management plan will be targeted toward specific problem species at specific times of year and may involve mixing and matching different deterrence strategies.

Natural areas near farmland can provide refuge for birds that contribute to natural pest control. However, birds can endanger food safety by defecating on or near produce. Work in the western US suggests that Campylobacter spp. are the potential foodborne pathogens most commonly associated with wild birds and that pathogen prevalence is higher in landscapes dominated by animal agriculture. However, relatively little is known about other fresh-market-produce growing regions. Working on produce farms in the Southeastern US, we characterized bird communities, tested bird feces deposited on crop foliage for Campylobacter and Salmonella, and searched for landscape features associated with heightened bird-associated food safety risks. We found that bird communities on farms were generally similar across ecoregions. Campylobacter was never detected from bird feces deposited on crop foliage, but Salmonella was detected in 8.6% of fecal samples. Salmonella prevalence in crop-surface-collected bird feces was highest when farms also produced livestock and when wetland cover was prevalent in the landscape. Overall, our results suggest that on-farm livestock production may be an indicator of bird-associated food safety risks in the Southeast, as in the West. We suggest there may be some similarities, but important differences, in food safety risks posed by birds in different US produce growing regions.

ContextConservation in working landscapes is critical for halting biodiversity declines and ensuring farming system sustainability. However, concerns that wildlife may carry foodborne pathogens has created pressure on farmers to remove habitat and reduce biodiversity, undermining farmland conservation. Nonetheless, simplified farming landscapes may host bird communities that carry higher foodborne disease risks.ObjectivesWe analyzed the effects of local farming practices and surrounding landscapes on bird communities and food-safety risks across 30 California lettuce farms. Specifically, we sought to determine how farmland diversification affects bird diversity, fecal contamination, and foodborne pathogen incidences, thereby identifying potential tradeoffs between managing farms for bird conservation versus food safety.MethodsWe surveyed birds at 227 point-count locations, quantified fecal contamination along 120 transects, and assayed 601 bird feces for pathogenic E. coli, Campylobacter spp., and Salmonella spp. We then used hierarchical models to quantify effects of farm management and landscape context on bird communities and food-safety risks.ResultsSurrounding ungrazed seminatural areas were associated with higher bird diversity, more species of conservation concern, and fewer flocks that may increase risks from foodborne pathogens. In contrast, on-farm diversification practices and surrounding grazing lands offered weaker bird conservation benefits. Surrounding grazed lands were associated with more potentially pathogenic bird feces in crop fields.ConclusionsOur results suggest that habitat conservation around produce farms could support bird conservation without increasing foodborne pathogens, especially on farms further from grazing lands. Thus, interventions that diversify farming systems offer potential to simultaneously conserve biodiversity and provide safe food for human consumption.

Wild birds pose a difficult food safety risk to manage because they can avoid traditional wildlife mitigation strategies, such as fences. Birds often use agricultural fields and structures as foraging and nesting areas, which can lead to defecation on crops and subsequent transfer of foodborne pathogens. To assess the food safety risk associated with these events, wild bird feces were collected from produce fields across the southeastern United States during the 2021 and 2022 growing seasons. In total 773 fecal samples were collected from 45 farms across Florida, Georgia, South Carolina, and Tennessee, and 2.1% (n = 16) of samples were Salmonella-positive. Importantly, 75% of Salmonella were isolated from moist feces, showing reduced Salmonella viability when feces dry out. 16S microbiome analysis showed that presence of culturable Salmonella in moist feces correlated to a higher proportion of the Enterobacteriaceae family. From the Salmonella-positive samples, 62.5% (10/16) contained multi-serovar Salmonella populations. Overall, 13 serovars were detected, including six most commonly attributed to human illness (Enteriditis, Newport, Typhimurium, Infantis, Saintpaul, and Muenchen). PCR screening identified an additional 59 Salmonella-positive fecal samples, which were distributed across moist (n = 44) and dried feces (n = 15). On-farm point counts and molecular identification from fecal samples identified 57 bird species, including for 10 Salmonella-positive fecal samples. Overall, there was a low prevalence of Salmonella in fecal samples, especially in dried feces, and we found no evidence of Salmonella transmission to proximal foliage or produce. Fecal samples collected in farms close together shared highly related isolates by whole genome sequencing and also had highly similar Salmonella populations with comparable relative frequencies of the same serovars, suggesting the birds acquired Salmonella from a common source.

Foodborne pathogens cause over 9 million illnesses in the United States each year, and Campylobacter from chickens is the largest contributor. Rearing poultry outdoors without the use of antibiotics is becoming an increasingly popular style of farming; however, little is understood about how environmental factors and farm management alter pathogen prevalence. Our survey of 27 farms in California, Oregon, Washington, and Idaho, USA, revealed a diversity of management practices used to rear poultry in the open environment. Here, we assess environmental and management factors that impact Campylobacter spp. prevalence in 962 individual chicken fecal samples from 62 flocks over a three-year period. We detected Campylobacter spp. in 250/962 (26.0%) of fecal samples screened, in 69.4% (43/62) of flocks, and on 85.2% (23/27) of farms. We found that Campylobacter spp. prevalence was predicted to increase in poultry on farms with higher average wind speeds in the seven days preceding sampling; on farms embedded in more agricultural landscapes; and in flocks typified by younger birds, more rotations, higher flock densities, and the production of broilers. Collectively, our results suggest that farms in areas with higher wind speeds and more surrounding agriculture face greater risk of Campylobacter spp. introduction into their flocks.

Diet composition modulates animals' ability to resist parasites and recover from stress. Broader diet breadths enable omnivores to mount dynamic responses to parasite attack, but little is known about how plant/prey mixing might influence responses to infection. Using omnivorous deer mice (Peromyscus maniculatus) as a model, we examine how varying plant and prey concentrations in blended diets influence resistance and body condition following infestation by Rocky Mountain wood ticks (Dermacentor andersoni). In two repeated experiments, deer mice fed for 4 weeks on controlled diets that varied in proportions of seeds and insects were then challenged with 50 tick larvae in two sequential infestations. The numbers of ticks successfully feeding on mice declined by 25% and 66% after the first infestation (in the first and second experiments, respectively), reflecting a pattern of acquired resistance, and resistance was strongest when plant/prey ratios were more equally balanced in mouse diets, relative to seed-dominated diets. Diet also dramatically impacted the capacity of mice to cope with tick infestations. Mice fed insect-rich diets lost 15% of their body weight when parasitized by ticks, while mice fed seed-rich diets lost no weight at all. While mounting/maintaining an immune response may be energetically demanding, mice may compensate for parasitism with fat and carbohydrate-rich diets. Altogether, these results suggest that a diverse nutritional landscape may be key in enabling omnivores' resistance and resilience to infection and immune stressors in their environments.

Generalist predators can enhance biological control by filling unique niches and complementing other natural enemies, or disrupt it by preying upon other predators and parasitoids, complicating their net value for biological control. We searched for evidence of complementarity and/or interference between native (primarily Eriopis chilensis and E. eschscholtzi) and exotic (primarily Hippodamia variegata and Harmonia axyridis) lady beetles attacking aphids in alfalfa (Medicago sativa) fields near Santiago, Chile. Across 60 fields and three growing seasons, exotic lady beetle adults and larvae reached peak abundance relatively earlier in the growing season than the natives. Furthermore, exotic lady beetle peaks aligned more closely with aphid peak abundance than did native lady beetle peaks. Abundances of native lady beetle adults and larvae were weakly positively correlated with those of exotics, and peak aphid densities were generally lowest in fields where native and non-native lady beetle adults were similarly abundant. Therefore, we did not see evidence of strong interference between exotics and natives. Natural-agricultural habitat edges reduced native, but not exotic, larval lady beetle lag behind aphid peaks and was associated with greater lady beetle and lower aphid densities. Moreover, farms embedded in landscapes with greater natural habitat cover supported more exotic, but not native, lady beetles, and increased the lag between larval lady beetles and aphids for natives but not exotics. These findings support the idea that farms embedded within mosaics of natural and agricultural habitats may provide greater interaction potential between native lady beetles and aphid pests on farms as they move across the landscape, leading to greater top -down control. In contrast, exotic lady beetle lags were unaffected by landscape composition or configuration, but their greater densities in farms surrounded by more natural habitats might reflect a 'concentration effect' whereby exotic lady beetle abundance becomes concentrated in the agricultural habitats that they prefer. Our findings suggest that some lady beetles introduced for biocontrol may be better adapted to intensively managed habitats than natives, possibly leading to spatiotemporal complementarity between native and exotic lady beetles.

Global temperatures are generally increasing, and this is leading to a well documented advancement and extension of seasonal activity of many pest insects. Effects of changing precipitation have received less attention, but might be complex because rain and snow are increasing in some places but decreasing in others. This raises the possibility that altered precipitation could accentuate, or even reverse, the effects of rising temperatures on pest outbreaks. We used >592 K aphid suction-trap captures over 15 years, in the heavily farmed central USA, to examine how the activity of Aphis glycines (soybean aphid), Rhopalosiphum maidis (corn aphid), and Rhopalosiphum padi (bird cherry-oat aphid) changed with variation in both temperature and precipitation. Increasing precipitation caused late-season flight activity of A. glycines and early-season activity of R. padi to shift earlier, while increasing temperature did the same for early-season activity of A. glycines and R. maidis. In these cases, precipitation and temperature exhibited directionally similar, but independent, effects. However, precipitation sometimes mediated temperature effects in complex ways. At relatively low temperatures, greater precipitation generally caused late-season flights of R. maidis to occur earlier. However, this pattern was reversed at higher temperatures with precipitation delaying late-season activity. In contrast, greater precipitation delayed peak flights of R. padi at lower temperatures, but caused them to occur earlier at higher temperatures. So, in these two cases the interactive effects of precipitation on temperature were mirror images of one another. When projecting future aphid flight phenology, models that excluded precipitation covariates consistently underpredicted the degree of phenological advance for A. glycines and R. padi, and underpredicted the degree of phenological delay for R. maidis under expected future climates. Overall, we found broad evidence that changing patterns of aphid flight phenology could only be understood by considering both temperature and precipitation changes. In our study region, temperature and precipitation are expected to increase in tandem, but these correlations will be reversed elsewhere. This reinforces the need to include both main and interactive effects of precipitation and temperature when seeking to accurately predict how pest pressure will change with a changing climate.

Abstract Open-environment poultry farms that allow chickens to forage outdoors are becoming increasingly common throughout the United States and Europe; however, there is little information regarding the diversity and prevalence of ectoparasites in these farming systems. Eight to 25 birds were captured and surveyed for ectoparasites on each of 17 farms across the states of Washington, Idaho, Oregon, and California. Among the farms sampled, six louse species (Phthiraptera: Ischnocera & Amblycera) and two parasitic mite species (Acari: Mesostigmata) were collected and identified: Goniodes gigas (Taschenberg, 1879; Phthiraptera: Menoponidae) on one farm, Menacathus cornutus (Schömmer, 1913; Phthiraptera: Menoponidae) on one farm, Menopon gallinae (Linnaeus, 1758; Phthiraptera: Menoponidae) on six farms, Lipeurus caponis (Linnaeus, 1758; Phthiraptera: Philopteridae) on five farms, Menacanthus stramineus (Nitzsch, 1818; Phthiraptera: Menoponidae) on nine farms, Goniocotes gallinae De Geer (Phthiraptera: Philopteridae) on 11 farms, Dermanyssus gallinae (De Geer, 1778; Mesostigmata: Dermanyssidae) on two farms, and Ornithonyssus sylviarum (Canestrini & Fanzago, 1877; Mesostigmata: Macronyssidae) on one farm. The diversity of ectoparasites on these open environment poultry farms highlights a need for additional research on ectoparasite prevalence and intensity in these poultry farming systems.

Recent declines in once-common species are triggering concern that an environmental crisis point has been reached. Yet, the lack of long abundance time series data for most species can make it difficult to attribute these changes to anthropogenic causes, and to separate them from normal cycles. Genetic diversity, on the other hand, is sensitive to past and recent environmental changes, and reflects a measure of a populations' potential to adapt to future stressors. Here, we consider whether patterns of genetic diversity among aquatic insects can be linked to historical and recent patterns of land use change. We collated mitochondrial cytochrome c oxidase subunit I (COI) variation for >700 aquatic insect species across the United States, where patterns of agricultural expansion and intensification have been documented since the 1800s. We found that genetic diversity was lowest in regions where cropland was historically (pre-1950) most extensive, suggesting a legacy of past environmental harm. Genetic diversity further declined where cropland has since expanded, even after accounting for climate and sampling effects. Notably though, genetic diversity also appeared to rebound where cropland has diminished. Our study suggests that genetic diversity at the community level can be a powerful tool to infer potential population declines and rebounds over longer time spans than is typically possible with ecological data. For the aquatic insects that we considered, patterns of land use many decades ago appear to have left long-lasting damage to genetic diversity that could threaten evolutionary responses to rapid global change.

BACKGROUNDGeneralist predators that kill and eat other natural enemies can weaken biological control. However, pest suppression can be disrupted even if actual intraguild predation is infrequent, if predators reduce their foraging to lower their risk of being killed. In turn, predator-predator interference might be frequent when few other prey are available, but less common when herbivorous and detritus-feeding prey are plentiful. We used molecular gut-content analysis to track consumption of the predatory bug Geocoris sp. by the larger intraguild predator Nabis sp., in organic and conventional potato (Solanum tuberosum) fields.RESULTSWe found that higher densities of both aphids and thrips, two common herbivores, correlated with higher probability of detecting intraguild predation. Perhaps, Nabis foraging for these herbivores also encountered and ate more Geocoris. Surprisingly, likelihood of intraguild predation was not strongly linked to densities of either Nabis or Geocoris, or farming system, suggesting a greater importance for prey than predator community structure. Intriguingly, we found evidence that Geocoris fed more often on the detritus-feeding fly Scaptomyza pallida with increasing predator evenness. This would be consistent with Geocoris shifting to greater foraging on the ground, where S. pallida would be relatively abundant, in the face of greater risk of intraguild predation.CONCLUSIONOverall, our findings suggest that while herbivorous prey may heighten intraguild predation of Geocoris in the foliage, detritivores might support a shift to safer foraging on the ground. This provides further evidence that prey abundance and diversity can act to either heighten or relax predator-predator interference, depending on prey species identity and predator behavior.

Growing demand for poultry meat and eggs labeled as organic, cage free, or pasture raised has increased the number of producers that manage chickens outdoors. In these open environments, there are likely diverse enteric parasites sustained by fecal-oral transmission or passage through intermediate invertebrate hosts (e.g., worms and insects) that chickens consume. Enteric parasites can reduce chicken health and productivity, but there are few published data describing the identities or prevalence of these parasites on farms that use open environments in the United States. We surveyed 27 poultry farms with open environments that were situated across a wide geographic range, including California, Oregon, Idaho, and Washington. These farms did not use anticoccidial drugs, coccidia vaccines, or parasiticides. Flock size, enclosure area, flock density, flock rotation frequency, and average flock age were highly correlated for all the farms in this study. We analyzed how enclosure size and flock rotations per year (which represented two axes of variation in management) correlated with prevalence of five observed parasite taxa at the farm level. Across all flocks, we detected by fecal flotation Eimeria spp. (95% flocks), Ascaridia galli (69%), Heterakis gallinarum (52%), Capillaria spp. (39%), Strongyloides avium (13%), tapeworm species (29%), Cryptosporidium spp. (3%), and Dispharynx nasuta (1%). Eighty-five percent of samples were coinfected with two or more parasite taxa. Sixty-seven percent of farms raised only layer chicken breeds, 4% raised only broiler breeds, and 30% raised both layer and broiler breeds. The average age of the broiler flocks was 11.0 wk (±1.1 SE), and flocks were moved 54.7 (±17.9) times annually to new locations in pastures (hereafter, "rotation"). Layer flocks averaged 84.9 (±7.67) wk of age and were moved less often on farms being rotated 20.0 (±6.05) times per year. Generalized linear mixed models indicated that for every 1 m2 increase in enclosure size, the odds of detecting Eimeria spp. increased by 0.03%. Furthermore, for every additional rotation per year, the odds of detecting A. galli decreased by 1.3%. For every additional rotation per year, the odds of detecting tapeworm species increased by 2.2%. We found no evidence that flock spatial management affected prevalence of the other parasites observed on the farms. Farming practices and parasite responses in these systems are highly varied, which makes it difficult to identify potential management interventions for reducing these infections.

Birds play many roles within agroecosystems including as consumers of crops and pests, carriers of pathogens and beloved icons. Birds are also rapidly declining across North America, in part due to agricultural intensification. Thus, it is imperative to identify how to manage agroecosystems to best support birds for multi-functional outcomes (e.g. crop production and conservation). Both the average amounts of services/disservices provided and their temporal stability are important for effective farm planning. Here, we conducted point count surveys for 4 years across 106 locations on 27 diversified farms in Washington and Oregon, USA. We classified birds as ecosystem service or disservice providers using indices spanning supporting, regulating, provisioning and cultural services/disservices. We then examined service/disservice index pairwise correlations and assessed the relative importance of local, farm and landscape complexity on the average and temporal stability of avian service/disservice provider indices. Generally, service provider indices (production benefitting birds, grower appreciation and conservation scores) were positively correlated with each other. Foodborne pathogen risk, grower disapproval and identity/iconic value indices were also positively correlated with each other. However, the crop damaging bird index generally had low correlations with other indices. Farms that implemented more conservation-friendly management practices generally had higher average service provider indices, but farm management did not impact disservice provider indices, except for grower disapproval. Average disservice provider indices were lower on farms in complex landscapes. Local vertical vegetation complexity tended to increase the temporal stability of service provider indices but did not affect the disservice provider indices. Greater landscape complexity was generally associated with increased temporal stability of service and disservice provider indices. Increased landscape complexity may stabilize bird communities by increasing bird community evenness, which in turn, positively predicted temporal stability of all service/disservice provider indices. Policy implications. Our results suggest that farmers can effectively manage their farms to harness ecosystem services from birds through farm diversification. Disservices provided by birds, however, appear to be most negatively impacted by landscape-level complexity. Thus, greater incentives for farmers to increase semi-natural cover at the landscape scale are likely necessary to achieve multifunctional outcomes for conservation and agriculture.

Recent foodborne illness outbreaks have heightened pressures on growers to deter wildlife from farms, jeopardizing conservation efforts. However, it remains unclear which species, particularly birds, pose the greatest risk to food safety. Using >11,000 pathogen tests and 1565 bird surveys covering 139 bird species from across the western United States, we examined the importance of 11 traits in mediating wild bird risk to food safety. We tested whether traits associated with pathogen exposure (e.g., habitat associations, movement, and foraging strategy) and pace-of-life (clutch size and generation length) mediated foodborne pathogen prevalence and proclivities to enter farm fields and defecate on crops. Campylobacter spp. were the most prevalent enteric pathogen (8.0%), while Salmonella and Shiga-toxin producing Escherichia coli (STEC) were rare (0.46% and 0.22% prevalence, respectively). We found that several traits related to pathogen exposure predicted pathogen prevalence. Specifically, Campylobacter and STEC-associated virulence genes were more often detected in species associated with cattle feedlots and bird feeders, respectively. Campylobacter was also more prevalent in species that consumed plants and had longer generation lengths. We found that species associated with feedlots were more likely to enter fields and defecate on crops. Our results indicated that canopy-foraging insectivores were less likely to deposit foodborne pathogens on crops, suggesting growers may be able to promote pest-eating birds and birds of conservation concern (e.g., via nest boxes) without necessarily compromising food safety. As such, promoting insectivorous birds may represent a win-win-win for bird conservation, crop production, and food safety. Collectively, our results suggest that separating crop production from livestock farming may be the best way to lower food safety risks from birds. More broadly, our trait-based framework suggests a path forward for co-managing wildlife conservation and food safety risks in farmlands by providing a strategy for holistically evaluating the food safety risks of wild animals, including under-studied species.

Birds increase crop yields via consumption of pests in some contexts but disrupt pest control via intraguild predation in others. Landscape complexity acts as an inconsistent mediator, sometimes increasing, decreasing, or not impacting pest control. Here, we examined how landscape context and seasonal variation mediate the impact of birds on arthropod pests and natural enemies, leaf damage, and yields of broccoli (Brassica oleracea) on highly diversified farms that spanned the USA west coast. Our study had two complementary components: a bird exclusion experiment and molecular diet analysis of 357 fecal samples collected from the most commonly captured bird species that also foraged in Brassica fields—American Goldfinch (Spinus tristis), American Robin (Turdus migratorius), Savannah Sparrow (Passerculus sandwichensis), Song Sparrow (Melospiza melodia), and White-crowned Sparrow (Zonotrichia leucophrys). Bird access yielded higher, rather than lower, numbers of pest aphids and increased their parasitism, while no other arthropods examined were consistently impacted. Independent of bird presence, percent natural cover in the landscape sometimes increased and sometimes decreased densities of arthropods in the mid-growth period, with diminishing impacts in the late-growth period. Herbivore feeding damage to broccoli leaves decreased with increasing amounts of natural land cover and in the late-growth period. Molecular diet analysis revealed that Brassica pests and predatory arthropods were relatively uncommon prey for birds. Landscape context did not alter the prey items found in bird diets. Altogether, our bird-exclusion experiment and molecular diet analysis suggested that birds have relatively modest impacts on the arthropods associated with broccoli plantings. More broadly, the limited support in our study for net natural pest control services suggests that financial incentives may be required to encourage the adoption of bird-friendly farming practices in certain cropping systems.

Generalist predators’ complex feeding relationships make it difficult to predict their contribution to pest suppression. Alternative prey can either distract predators from attacking pests, weakening biocontrol, or provide food that support larger predator communities to enhance it. Similarly, predator species might both feed upon and complement one another by occupying different niches. Here, we use molecular gut-content analysis to examine predation of western flower thrips (Frankliniella occidentalis) by two generalist predatory bugs, Geocoris sp. and Nabis sp. We collected predators from conventional and organic potato fields that differed in arthropod abundance and composition, so that we could draw correlations between abundance and biodiversity of predators and prey, and thrips predation. We found that alternative prey influenced the probability of detecting Geocoris predation of thrips through a complex interaction. In conventionally-managed potato fields, thrips DNA was more likely to be detected in Geocoris as total abundance of all arthropods in the community increased. But the opposite pattern was found in organic fields, where the probability of detecting thrips predation by Geocoris decreased with increasing total arthropod abundance. Perhaps, increasing abundance (from a relatively low baseline) of alternative prey triggered greater foraging activity in conventional fields, but drew attacks away from thrips in organic fields where prey were consistently relatively bountiful. The probability of detecting Geocoris predation of thrips generally increased with increasing thrips density, but this correlation was steeper in organic than conventional fields. For both Geocoris and Nabis, greater Nabis abundance correlated with reduced probability of detecting thrips DNA; for Nabis this was the only important variable. Nabis is a common intraguild predator of the smaller Geocoris, and is highly cannibalistic, suggesting that predator-predator interference increased with more Nabis present. Complex patterns of thrips predation seemed to result from a dynamic interaction with alternative prey abundance, alongside consistently negative interactions among predators. This provides further evidence that alternative prey and predator interference must be studied in concert to accurately predict the contributions of generalists to biocontrol.

1. Farmland birds can suppress insect pests, but may also consume beneficial insects, damage crops and potentially carry foodborne pathogens. As bird communities shift in response to farming practices, so too do the benefits (services) and costs (disservices) from birds. Understanding how and why ecosystem services and disservices covary can inform management interventions that enhance synergies, avoid trade-offs and promote multifunctionality. 2. We investigated how farmland diversification practices influence the services and disservices provided by wild birds on 21 California strawberry farms. Specifically, we coupled 285 bird surveys, metabarcoding and other molecular analyses of 4,000 faecal samples representing 55 bird species (mostly passerines) to determine which individuals consumed pests, natural enemies, and crops and carried foodborne pathogens. Then, we explored how farming practices shape ecosystem service bundles, or suites of consistently co-occurring services/disservices. 3. Avian services and disservices were shaped by interactions between local farming practices and landscape context. We found that the amount of semi-natural habitat surrounding each farm was the single most important driver of ecosystem services, with the best outcomes (highest multifunctionality) occurring on farms surrounded by semi-natural habitat. 4. Bundles were primarily influenced by landscape context. Increasing semi-natural habitat around farms was associated with more multifunctional bird communities that maximized services and minimized disservices. However, not all trade-offs were minimized in landscapes with more semi-natural habitat, suggesting that specific farming contexts can exacerbate or mitigate trade-offs as bird communities shift in response to diversification practices. 5. Synthesis and applications. Though growers are often pressured to remove non-crop habitat to reduce food-safety risks, our work suggests that conserving habitat can support bird conservation, mitigate food-safety risks and decrease crop damage from birds. More broadly, by considering the multiple roles that communities play in ecosystems, managers can simultaneously maximize services and minimize disservices to achieve multifunctionality.

Growers may be more likely to adopt wildlife-friendly practices if they perceive that beneficial species are present and conservation actions are successful. At the same time, a farm's landscape and regional context may influence whether biodiversity, including wild birds, are likely to provide ecosystem services or disservices. Here, across two Bird Conservation Regions in the western USA, we assessed a feedback loop that links growers' attitudes towards birds, farming practices, and bird assemblages' hypothesized impacts. To do so, we paired a grower questionnaire survey, bird point count surveys, and farm management and landscape classifications. We found that growers generally exhibited more positive attitudes towards raptors than songbirds and allies (e.g., flycatchers, woodpeckers, hummingbirds). Attitudes towards raptors were more positive when farms were embedded in more natural landscapes and had greater proportions of nonnative birds. Growers held more positive attitudes towards songbirds and allies related to production (yields, crop quality, insect control) when their farms were in the Northern Pacific Rainforest region and were embedded in more natural landscapes. Growers' attitudes towards songbirds and allies related to disease/infrastructure (food safety, animal disease, building/machinery damage, vertebrate control) were more positive in the Northern Pacific Rainforest region as landscapes became more natural, but these relationships did not hold for Coastal California. However, growers' attitudes towards birds were mostly unrelated to the practices used on the farm. Understanding these feedback loops is crucial to increasing uptake of and retention in conservation programs for rapidly declining farmland bird communities.

Greater arthropod diversity may promote biological control by bringing together predator species that occupy complementary feeding niches. Diverse prey communities could further accentuate such niche differences and decrease predator-predator antagonism. However, much evidence of these effects comes from simple experiments that do not reflect the ecological complexity of real agricultural fields. Here we used molecular gut-content analysis to examine how predator and prey biodiversity impacted consumption of aphids by two generalists, Nabis sp. and Geocoris sp., in potato (Solanum tuberosum) crops. We show that both predator species were more likely to have fed on aphids when they foraged in fields with greater overall predator richness, an apparent benefit of predator biodiversity for aphid biocontrol consistent with greater complementarity. However, Geocoris saw less-frequent aphid predation with increasing predator evenness, perhaps because they foraged less when dangerous intraguild predators were common. For both predator species, higher thrips (Frankliniella occidentalis) abundance also correlated with greater aphid predation, as did higher total arthropod richness for Nabis. Altogether, beneficial complementarity appeared to be enhanced by greater predator or prey richness, although, for Geocoris, this was opposed by a negative effect of predator evenness. Strong prey-species-identity effects generally enhanced, rather than disrupted, aphid predation. Overall, the full diversity of biodiversity-biocontrol relationships suggested by smaller-scale experiments also appeared to be impactful in complex, working agricultural fields.

Natural enemies often move among habitats to track prey and resources. Indeed, biocontrol often depends on natural enemies dispersing into crops after disturbances such as tillage and pesticide applications. However, the small size of many natural enemies makes it difficult to observe such movements. Here we used genetic relatedness among entomopathogenic nematodes, tiny, soil-dwelling, and thus cryptic natural enemies, to infer their movement across an agricultural landscape. We collected strains of two nematode species, Heterorhabditis bacteriophora and Steinernema feltiae, by placing sentinel hosts into eight irrigated Solanum tuberosum fields across arid central Washington State. We then used restriction site associated DNA sequencing to generate single nucleotide polymorphisms and infer relatedness among strains across our study sites. We identified 3,367 and 138,286 polymorphic loci for H. bacteriophora and S. feltiae, respectively. Genetic differentiation for both species increased with greater distance between sites, although there was considerable variation. While strains collected from the same field were generally more closely related than those from different sites, for both species, strains from different fields were sometimes quite closely related. Altogether, our results suggest a surprising amount of genetic similarity among nematodes from distant sites, despite the presumably limited distances that can be traversed by individual worms. This is consistent with the nematodes moving, at least occasionally, between far-apart locations. More generally, we suggest that recent advances in population genomics are providing powerful new tools for mapping natural enemy movement across broad landscapes.