Agricultural intensification is a leading threat to bird conservation. Highly diversified farming systems that integrate livestock and crop production might promote a diversity of habitats useful to native birds foraging across otherwise-simplified landscapes. At the same time, these features might be attractive to nonnative birds linked to a broad range of disservices to both crop and livestock production. We evaluated the influence of crop-livestock integration on wild bird richness and density along a north-south transect spanning the U.S. West Coast. We surveyed birds on 52 farms that grew primarily mixed vegetables and fruits alone or integrated livestock into production. Crop-livestock systems harbored higher native bird density and richness relative to crop-only farms, a benefit more pronounced on farms embedded in nonnatural landscapes. Crop-livestock systems bolstered native insectivores linked to the suppression of agricultural pest insects but did not bolster native granivores that may be more likely to damage crops. Crop-livestock systems also significantly increased the density of nonnative birds, primarily European Starlings (Sturnus vulgaris) and House Sparrows (Passer domesticus) that may compete with native birds for resources. Models supported a small, positive correlation between nonnative density and overall native bird density as well as between nonnative density and native granivore density. Relative to crop-only farms, on average, crop-livestock systems exhibited 1.5 times higher patch richness, 2.4 times higher density of farm structures, 7.3 times smaller field sizes, 2.4 times greater integration of woody crops, and 5.3 times greater integration of pasture/hay habitat on farm. Wild birds may have responded to this habitat diversity and/or associated food resources. Individual farm factors had significantly lower predictive power than farming system alone (change in C statistic information criterion (ΔCIC) = 80.2), suggesting crop-livestock systems may impact wild birds through a suite of factors that change with system conversion. Collectively, our findings suggest that farms that integrate livestock and crop production can attract robust native bird communities, especially within landscapes devoted to intensified food production. However, additional work is needed to demonstrate persistent farm bird communities through time, ecophysiological benefits to birds foraging on these farms, and net effects of both native and nonnative wild birds in agroecosystems.

中文翻译：

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高度多样化的农畜养殖系统重塑了野生鸟类群落。

农业集约化是鸟类保护的主要威胁。将牲畜和农作物生产结合起来的高度多样化的耕作制度可能会促进多种多样的栖息地，这些栖息地有益于本地鸟类在其他简化的景观中觅食。同时，这些特征可能对与农作物和牲畜生产造成广泛损害有关的非本地鸟类具有吸引力。我们评估了农作物-畜牧业整合对横跨美国西海岸的南北横断面野生鸟类丰富度和密度的影响。我们调查了52个农场的鸟类，这些农场主要单独种植蔬菜和水果，或将牲畜纳入生产。相对于仅种植农作物的农场来说，农牧系统具有更高的原生鸟类密度和丰富度，这对于埋藏在非自然景观中的农场来说更为明显。作物－畜牧系统增强了与抑制农业害虫有关的原生食虫，但并未增强可能更可能损害农作物的原生食虫。作物-牲畜系统也显着提高了非本地鸟类的密度，主要是欧洲八哥（Sturnus vulgaris）和麻雀（Passer domesticus），它们可能与本地鸟类竞争资源。模型支持非自然密度和总体自然鸟类密度之间以及非自然密度和自然食肉动物密度之间的小正相关。相对于仅种植作物的农场，平均而言，农作物-牲畜系统的斑块丰富度高1.5倍，农场结构密度高2.4倍，田间面积小7.3倍，木本作物整合度高2.4倍，以及5。牧场上的干草/干草栖息地一体化程度提高了3倍。野生鸟类可能已经对这种栖息地的多样性和/或相关的食物资源做出了反应。单个农场因素的预测能力远低于单独的耕作系统（C统计信息标准（ΔCIC）= 80.2），表明农作物－牲畜系统可能会通过一系列随系统转换而变化的因素影响野生鸟类。总体而言，我们的发现表明，将牲畜与农作物生产结合起来的农场可以吸引强大的本地鸟类群落，尤其是在致力于集约化粮食生产的景观中。但是，还需要做更多的工作来证明长期以来农场中鸟类的持久性，在这些农场上觅食对鸟类的生态生理益处以及农业生态系统中本地和非本地野生鸟类的净效应。