Assessing the influence of raptors on grape-eating birds in a Mediterranean vineyard

Several bird species may cause serious damage to grape production. The ability of raptors as biological control agents of grape-eating birds is poorly understood and under-used. We installed artificial nests and perches to encourage the presence and activity of raptors in vineyards located in central Spain and explored their effectiveness to reduce damage to grapes. We characterized the raptor community by field surveys and assessment of natural breeding sites, evaluated the abundance of grape-eating birds, and sampled damage to grape production for three consecutive years. Raptor community in the study area was diverse (13 species). Breeding of ornitophagous species such as Booted eagle Hieraaetus pennatusand Northern goshawk Accipiter gentilis was confirmed in the forest patches. We identified 10 grape-eating bird species, with Spotless starling (Sturnus unicolor) being the most abundant. Distance from the edges between vineyards and natural and semi-natural woody vegetation affected damage to grapes, with more damage close to the edges. The installed elements did not significantly reduce damage to grapes. Woody vegetation in and around the vineyards may reduce the success of the installed elements by providing shelter to grape-eating birds and suitable sites for raptor breeding and perching. Other variables such as vine orientation, land-cover, and distance to raptor nests did not affect damage to grapes. To promote the conservation of raptors and their regulating services in this Mediterranean agroforestry system, more research is needed to find methods to increase the presence of raptors in vineyards and to manage the woody shelters used by grape-eating birds around crops.

多种鸟类会对葡萄生产造成严重危害。猛禽（raptor）作为食葡萄鸟类的生物防治因子，其应用潜力目前尚未得到充分认知与推广。我们在西班牙中部的葡萄园搭建人工巢箱与栖木，以吸引猛禽在此栖息活动，并探究其降低葡萄受害程度的效果。通过野外调查与天然繁殖位点评估，我们对研究区域的猛禽群落进行了特征描述，同时对食葡萄鸟类的种群丰度开展评估，并连续三年对葡萄生产受害情况进行采样监测。本研究区域的猛禽群落具有较高多样性，共计13个物种。森林斑块中已确认食鸟猛禽物种（如靴隼雕（Hieraaetus pennatus）与苍鹰（Accipiter gentilis））的繁殖活动。本次研究共记录到10种食葡萄鸟类，其中以纯色椋鸟（Sturnus unicolor）的种群丰度最高。葡萄园与天然、半天然木本植被的交界距离会影响葡萄受害程度，靠近交界区域的葡萄受害更为严重。搭建的人工设施并未显著降低葡萄受害程度。葡萄园内部及周边的木本植被，可为食葡萄鸟类提供庇护，同时为猛禽提供繁殖与栖息的适宜场所，因此可能会削弱人工搭建设施的防控效果。其余变量，如葡萄藤种植朝向、土地覆被类型以及距猛禽巢址的距离，均未对葡萄受害程度产生显著影响。为在该地中海农林业系统中推动猛禽保护及其生态调控服务的发展，未来仍需开展更多研究，以探索提升葡萄园猛禽种群数量的方法，并对作物周边食葡萄鸟类赖以栖息的木本植被开展针对性管理。