Barn Owl Breeding Napa Valley California

Conservation of uncultivated habitats can increase the potential for ecosystem services in agroecosystems, but these lands are also susceptible to wildfires in the arid western United States. In Napa Valley, California, abundant rodent pests and an interest in integrated pest management have led wine producers to use nest boxes to attract Barn Owls (Tyto furcata) to winegrape vineyards. The viability of this practice as a method to control rodent pests depends heavily on the amount of hunting effort that Barn Owls expend in vineyards, which is known to be influenced by the amount of uncultivated land cover types surrounding the nest box. Wildfires burned nearly 60,000 ha of mainly urban and uncultivated lands surrounding Napa Valley in 2017, altering Barn Owl habitats. We compared GPS tracking data from 32 Barn Owls nesting in 24 individual nest boxes before and after the fires to analyze their hunting habitat selection. Owls with burned areas available to them after the fires had home ranges that shifted towards the fires, but selection was not strongly associated with burned areas. Though there was some spatial use of burned areas, selection of land cover types was similar for birds before and after the fires and in burned and unburned areas. The strongest selection was for areas closest to the nest box and most recorded locations were in grassland, though selection indicated that owls used land cover types in proportion to their availability. Overall, habitat selection was resilient to changes caused by wildfires. These results are important for farmers who use nest boxes as a means of rodent control, which may be affected after dramatic disturbance events, especially as wildfires increase in the western United States.未开垦生境的保护可提升农业生态系统的生态系统服务潜力，但此类土地在美国西部干旱区域亦易受野火侵袭。在加利福尼亚州纳帕谷，当地啮齿类害虫问题频发，且酿酒生产者对有害生物综合治理（integrated pest management）的关注度持续提升，促使他们在酿酒葡萄园中布设巢箱以吸引仓鸮（Tyto furcata）。该生物防治手段的可行性，很大程度上取决于仓鸮在葡萄园中的捕猎投入量，而该捕猎投入已被证实会受巢箱周边未开垦土地覆被类型的影响。2017年，野火烧毁了纳帕谷周边近6万公顷土地，其中以城市用地与未开垦生境为主，此举改变了仓鸮的栖息生境。我们对比了32只分别在24个独立巢箱中筑巢的仓鸮在野火前后的GPS追踪数据，以分析其捕猎生境选择偏好。野火后可利用火烧区域的仓鸮，其家域范围向火烧区域偏移，但生境选择并未与火烧区域呈现强相关性。尽管部分仓鸮会对火烧区域进行空间利用，但无论野火前后，或是在火烧与未火烧区域中，仓鸮对土地覆被类型的选择模式均保持一致。仓鸮对距巢箱最近的区域表现出最强的选择偏好，绝大多数记录到的活动点位均位于草地中，不过其对土地覆被类型的利用整体符合可获得性比例。总体而言，仓鸮的生境选择对野火引发的生境变化具有恢复力。该研究结果对采用巢箱开展啮齿类害虫防治的农户具有重要参考价值——此类生物防治手段可能在极端干扰事件后受到影响，而随着美国西部野火发生频率的不断升高，该问题将愈发凸显。