Data from: Arthropod but not bird predation in Ethiopian homegardens is higher in tree-poor than in tree-rich landscapes

Bird and arthropod predation is often associated with natural pest control in agricultural landscapes, but the rates of predation may vary with the amount of tree cover or other environmental factors. We examined bird and arthropod predation in three tree-rich and three tree-poor landscapes across southwestern Ethiopia. Within each landscape we selected three tree-rich and three tree-poor homegardens in which we recorded the number of tree species and tree stems within 100 × 100 m surrounding the central house. To estimate predation rates, we attached plasticine caterpillars on leaves of two coffee and two avocado shrubs in each homegarden, and recorded the number of attacked caterpillars for 7–9 consecutive weeks. The overall mean daily predation rate was 1.45% for birds and 1.60% for arthropods. The rates of arthropod predation varied among landscapes and were higher in tree-poor landscapes. There was no such difference for birds. Within landscapes, predation rates from birds and arthropods did not vary between tree-rich and tree-poor homegardens in either tree-rich or tree-poor landscapes. The most surprising result was the lack of response by birds to tree cover at either spatial scale. Our results suggest that in tree-poor landscapes there are still enough non-crop habitats to support predatory arthropods and birds to deliver strong top-down effect on crop pests.农业景观中，鸟类与节肢动物的捕食作用通常与自然虫害防控紧密关联，但捕食速率会随林木覆盖度或其他环境因素发生变化。本研究在埃塞俄比亚西南部的3个林木丰富型与3个林木匮乏型景观中开展了鸟类与节肢动物捕食作用调查。我们在每个景观内选取3个林木丰富型和3个林木匮乏型家庭菜园，记录中心住宅周边100m×100m样地内的树木物种数与茎干数。为估算捕食速率，我们在每个家庭菜园的2株咖啡灌木与2株鳄梨灌木的叶片上放置橡皮泥毛毛虫，并连续7至9周记录受攻击的毛毛虫数量。整体日均捕食速率为鸟类1.45%、节肢动物1.60%。节肢动物捕食速率在不同景观间存在显著差异，且在林木匮乏型景观中更高；但鸟类捕食速率并无此类差异。在景观内部，无论所在景观为林木丰富型还是匮乏型，鸟类与节肢动物的捕食速率在林木丰富型与匮乏型家庭菜园间均无显著差异。最出乎意料的研究结果是，无论在何种空间尺度下，鸟类捕食速率均未对林木覆盖度产生响应。本研究结果表明，在林木匮乏型景观中，仍存在足够的非作物生境支撑捕食性节肢动物与鸟类种群，从而对作物害虫产生显著的下行调控效应。