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  × 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.

中文翻译：

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物种相互作用和养殖环境的变化介导了鸟类在农业生态系统中的净效应。

有些鸟类被视为农田中的害虫和食源性病原体的媒介，但鸟类也通过食用害虫而使种植者受益。尽管许多种植者试图阻止鸟类进入其农场，但很少有研究试图量化鸟类服务和损害的净效应，更不用说净效应如何在农场管理策略之间转移。我们量化了鸟类对整个20株加州草莓（Fragaria  ×  ananassa）作物产量的净影响）农场的当地管理方式和景观环境各异。我们调查了农场的浆果破坏和鸟类掉落（作为病原体的潜在来源），并实施了大规模排除实验以量化鸟类对生产的影响。我们发现，鸟类对草莓生产的总体影响仅有轻微的负面影响，使经济价值降低了3.6％。鸟类的直接损害和行会内部的捕食同样对这一净效应作出了贡献，强调了间接营养相互作用的重要性，这种相互作用对种植者来说可能不太明显。在简单的景观中（例如，周围半自然栖息地的比例很小），鸟类在​​农田内部提供了害虫控制，并且鸟类受到的损害使农作物的收成达到了峰值。在复杂的景观中（例如，半自然栖息地的比例很高），鸟类以公会内捕食者为食更容易破坏害虫的控制。尽管如此，半自然的栖息地削弱了鸟类的服务和伤害，我们的模型预测，去除农田周围的栖息地将使鸟类对农作物造成的损失增加多达76％。作物的粪便污染极为罕见（0.01％）。但是，在围栏和铁丝密度较高的地方，粪便污染和鸟类破坏的确增加了，而那里经常有鸟类栖息。我们的结果表明，在农场周围维持半自然栖息地可能会增加鸟类的多样性并减轻鸟类的伤害，而不会增加食品安全风险。我们还表明，鸟类的净效应取决于养殖环境，并且相对于农场内的位置，当地农场的属性以及周围的景观以复杂的方式变化。