Data from: Canopy tree preference by insectivorous birds in shade-coffee farms: implications for migratory bird conservation

Land converted to coffee agriculture occupies >5 million hectares of what was once prime overwintering natural habitat in the American Neotropics for migrating birds. When tree canopy is retained or restored (i.e. shade-grown), coffee farms can serve as habitat refuge for wildlife. Yet few studies have examined whether canopy tree identity impacts habitat quality for biodiversity. Specifically, whether or not certain tree species are disproportionately important for foraging insectivorous birds remains unclear. In this study, we quantified bird foraging activity on 22 tree species in two Latin American Bird Friendly© coffee farms. Specifically, we conducted timed observations on focal trees to determine 1) tree preferences, 2) foraging bird abundance, 3) foraging time, and 4) species richness of birds using each canopy tree species. We found that birds did not forage randomly, and instead exhibited preferences for particular native tree species. Nitrogen-fixing Fabaceae were consistently used more frequently, supported more resident and migratory birds for longer periods of time, and supported more bird species than trees in other families. We posit that the potential mechanism contributing to tree preferences is the increase in insect abundance and diversity that provide high quality food for insectivores but do not present pest problems for coffee. Thus, tree species that support insects may provide multiple benefits for farmers in the form of bottom-up soil fertilization and top-down pest control. This study provides evidence that agroforestry land can be improved for birds of conservation concern by prioritizing canopy tree species that help birds and farm productivity.转为咖啡种植用途的土地总面积逾500万公顷，这些土地曾是美洲新热带区迁徙鸟类的优质越冬自然栖息地。若保留或修复林冠层（即采用遮阴种植模式），咖啡农场可成为野生生物的栖息地庇护所。然而目前鲜有研究探讨林冠树种的组成是否会影响生物多样性的栖息地质量，具体而言，特定树种是否对食虫鸟类的觅食活动具有不成比例的重要性，这一问题仍未明确。本研究针对两处拉丁美洲的鸟类友好型（Bird Friendly©）咖啡农场中的22个树种，量化了鸟类的觅食活动情况。具体而言，研究人员通过对目标树种开展计时观测，以明确四个核心观测维度：1）鸟类对树种的偏好性；2）觅食鸟类的种群丰度；3）单次觅食时长；4）利用各林冠树种的鸟类物种丰富度。研究结果显示，鸟类的觅食活动并非随机发生，而是对特定本土树种表现出显著偏好。相较于其他科属的树木，具有固氮能力的豆科（Fabaceae）树种始终被鸟类更频繁地利用，能够在更长时段内承载更多留鸟与迁徙鸟类，并支持更多鸟类物种生存。我们推测，导致鸟类产生树种偏好的潜在机制在于：这类固氮树种可提升昆虫的种群丰度与物种多样性，既为食虫鸟类提供了优质食物来源，又不会对咖啡种植造成虫害问题。因此，能够支撑昆虫种群的树种可从两个层面为种植者带来多重效益：一是通过自下而上的途径为土壤施肥，二是通过自上而下的方式实现虫害防控。本研究证实，通过优先选择既能助力鸟类保护、又能提升农场生产效益的林冠树种，可改善农林业用地对具有保育价值鸟类的承载能力。