Synergistic impacts of aggressive species on small birds in a fragmented landscape

1. Attempts to conserve threatened species in fragmented landscapes are often challenging because factors such as habitat loss, habitat degradation and dominant species interact to reduce threatened species’ capacity to survive and reproduce. Understanding how threatening and mitigating processes interact is critical if conservation measures are to be effective. 2. We used data from long-term monitoring of bird populations and multivariate latent variable models to quantify how Australian woodland birds respond to the presence of the Noisy Miner, a despotic species known to exclude other bird species. We then investigated the extent to which the presence of other aggressive species exacerbates the impacts of the Noisy Miner, and to what extent these impacts can be mitigated by dense midstorey plantings. 3. We found strong synergies between the Noisy Miner and two other aggressive species (Grey Butcherbird and Pied Butcherbird), despite weak effects of butcherbirds in isolation. ...1. 在破碎化景观中开展受威胁物种（threatened species）保护工作往往颇具挑战，因栖息地丧失（habitat loss）、栖息地退化（habitat degradation）与优势种（dominant species）等多重因素相互作用，会削弱受威胁物种的生存与繁殖能力。若要保障保护措施的有效性，明晰威胁过程与缓解过程的相互作用机制至关重要。 2. 本研究借助鸟类种群长期监测数据与多变量潜变量模型（multivariate latent variable models），量化了澳大利亚林地鸟类对噪钟鹊（Noisy Miner）的响应模式——该物种为已知会排挤其他鸟类的统治性物种。随后，我们探究了其他攻击性物种的存在会在多大程度上加剧噪钟鹊的负面影响，以及密植中层植被可在多大程度上缓解此类影响。 3. 研究发现，尽管钟鹊单独作用时的影响较为微弱，但噪钟鹊与另外两种攻击性物种——灰钟鹊（Grey Butcherbird）和斑钟鹊（Pied Butcherbird）之间存在显著的协同效应。