Camera trap data suggest uneven predation risk across vegetation types in a mixed farmland landscape

Ground-nesting farmland birds such as the grey partridge (Perdix perdix) have been rapidly declining due to a combination of habitat loss, food shortage and predation. Predator activity is the least understood factor, especially its modulation by landscape composition and complexity. An important question is whether agri-environment schemes such as flower strips are potentially useful for reducing predation risk, e.g., from red fox (Vulpes vulpes). We employed 120 camera traps for two summers in an agricultural landscape in Central Germany to record predator activity (i.e., the number of predator captures) as a proxy for predation risk and used generalized linear mixed models (GLMMs) to investigate how the surrounding landscape affects predator activity in different vegetation types (flower strips, hedges, field margins, winter cereal and rapeseed fields). Additionally, we used 48 cameras to study the distribution of predator captures within flower strips. Vegetation type was the most important factor determining the number of predator captures and captures rates in flower strips were lower than in hedges or field margins. Red fox capture rates were the highest of all predators in every vegetation type, confirming their importance as a predator for ground-nesting birds. The number of fox captures increased with woodland area and decreased with structural richness and distance to settlements. In flower strips, capture rates in the centre were approximately 9 times lower than at the edge. We conclude that the optimal landscape for ground-nesting farmland birds seems to be open farmland with broad extensive vegetation elements and a high structural richness. Broad flower blocks provide valuable, comparatively safe nesting habitats and the predation risk can further be minimized by placing them away from woods and settlements. Our results suggest that adequate landscape management may reduce predation pressure. 

Methods
Detailed information on data sampling and processing can be found in the article:
Laux, A., Waltert, M., Gottschalk, E. Camera trap data suggest uneven predation risk across vegetation types in a mixed farmland landscape. Ecology and Evolution.

地栖筑巢农田鸟类（如灰山鹑（Perdix perdix））的种群正快速衰退，其成因涵盖栖息地丧失、食物短缺与捕食作用的多重影响。其中捕食者活动是研究最为薄弱的环节，尤其是景观组成与复杂度对其的调控机制。一个核心科学问题在于，诸如花带（flower strips）这类农业环境计划，是否可用于降低诸如赤狐（Vulpes vulpes）带来的捕食风险。

本研究于德国中部的农业景观中，连续两个夏季布设120台相机陷阱（camera trap），以捕食者捕获次数作为捕食风险的替代指标记录其活动情况；同时采用广义线性混合模型（generalized linear mixed models, GLMMs），探究周边景观如何调控不同植被类型（花带、树篱、田埂、冬谷类作物田与油菜田）内的捕食者活动。此外，我们额外布设48台相机陷阱，以解析捕食者捕获点在花带内部的空间分布特征。

研究结果显示，植被类型是决定捕食者捕获次数的最关键因子，花带内的捕获率显著低于树篱或田埂。在所有植被类型中，赤狐的捕获率均为最高，证实了其作为地栖筑巢鸟类主要捕食者的重要地位。赤狐的捕获次数随林地面积占比增加而升高，随景观结构复杂度与距居民点距离增加而降低。在花带内部，中心区域的捕获率约为边缘区域的1/9。

综上，适合地栖筑巢农田鸟类的理想景观应为具备广泛粗放型植被元素与高结构复杂度的开阔农田。大面积花带能够提供兼具生态价值与相对安全性的筑巢栖息地，若将其设置在远离林地与居民点的区域，还可进一步压低捕食风险。本研究结果表明，合理的景观管理策略能够有效减轻捕食压力。

研究方法
详细的数据采样与处理流程可参阅以下文献：
Laux, A., Waltert, M., Gottschalk, E. 相机陷阱数据揭示混合农田景观中不同植被类型间的捕食风险不均一性. 《生态学与进化》（Ecology and Evolution）