Avian Response to Hurricane Maria in Coffee Plantations

Insights on impacts and resiliency of avian species with respect to hurricanes in the Caribbean have largely focused on responses measured in protected habitats. We assessed avian responses in non-protected habitat, specifically shade-restored coffee plantations, because their structural complexity retains many attributes of secondary forests, and may contribute to landscape scale species resiliency. We tallied species richness and estimated occupancy probability of 12 resident avian species, after adjusting for imperfect detection, to assess the impact of hurricane Maria (20 September 2017) in shade-restored coffee plantations. For five of those species, we also estimated local colonization and extinction probabilities to assess their prospect of rebounding (resiliency) in the context of two stages of shade restoration. We used survey data collected March-June 2015-2017 (pre-hurricane) and 2018 (post-hurricane) in 58 coffee farms and satellite imagery to assess vegetation structure. Restored farms were grouped into two categories based on time-since-restoration: newly-restored and fully-restored. We predicted that mean percent forest cover in fully-restored farms (~30-40%) would revert to levels in newly-restored farms (<15%), with concomitant changes in occupancy by avian species. As predicted, mean percent forest cover (16.17 ± 4.27%) in fully-restored farms post-hurricane reverted to pre-hurricane levels in newly-restored farms (15.00 ± 5.61%). The loss represented 30-38% relative to the pre-hurricane cover levels. Detections of focal species dropped an average of 41% post-hurricane, with associated reductions in occupancy for 9/11 species. Occupancy of the Puerto Rican Bullfinch and Puerto Rican Spindalis reverted to levels detected in newly-restored plantations prior to the hurricane as predicted. Prospects of rebounding were more likely for species with invariant or increases in colonization probability (e.g., Yellow-faced Grassquit, Northern Mockingbird, Puerto Rican Spindalis). Rebounding for frugivores like the Puerto Rican Bullfinch would be protracted given that colonization rates dropped from 0.56 ± 0.12 (pre-hurricane) to 0.04 ± 0.2 (post-hurricane), regardless of restoration stage. Our work showed that the avian community associated with restored coffee farms exhibited a high degree of ecological resistance as the similarity in species composition before and after the hurricane was 81%, and all 12 focal species continued to occupy farms under both restoration stages. The prospect of the focal species to rebound (resiliency) was species-specific, and in some cases, mediated by their affinity to a particular farm restoration stage. The strength of hurricanes is projected to intensify with global warming. Pockets of undamaged or partially damaged shade-grown or fully-restored coffee plantations may contribute to species resiliency by increasing landscape level habitat redundancy, and facilitate habitat shifts to secure food resources or harbor source populations to colonize recovering, hurricane-damaged habitat tracts.目前针对加勒比地区飓风对鸟类的影响及其种群恢复力的研究，大多聚焦于保护地栖息地内的鸟类响应。我们此次研究评估了非保护地栖息地——尤其是遮阴修复咖啡种植园（shade-restored coffee plantations）——中的鸟类响应，这类种植园的结构复杂性保留了次生林的诸多特征，或可在景观尺度上助力物种恢复力。 我们针对58个咖啡农场，整合2015-2017年3月至6月（飓风前）与2018年（飓风后）的调查数据，结合卫星影像评估植被结构，统计了12种留鸟的物种丰富度，并校正不完全检测（imperfect detection）后估算其占用概率（occupancy probability），以评估飓风玛丽亚（2017年9月20日）对遮阴修复咖啡种植园的影响。其中针对5个物种，我们还估算了局域定殖与灭绝概率，以分析它们在两个遮阴修复阶段下的种群恢复前景。 我们将修复后的农场按修复时长划分为两类：新修复农场与完全修复农场。我们曾提出假设：完全修复农场的平均森林覆盖率约为30%~40%，其将回落至新修复农场的水平（<15%），并伴随鸟类物种占用率的相应变化。 正如假设所示，飓风过后完全修复农场的平均森林覆盖率为16.17 ± 4.27%，回落至新修复农场飓风前的水平（15.00 ± 5.61%），相较飓风前的覆盖率损失了30%~38%。飓风后焦点物种的检测率平均下降了41%，11个物种中有9个的占用率出现了相应下降。波多黎各牛雀（Puerto Rican Bullfinch）与波多黎各食籽雀（Puerto Rican Spindalis）的占用率，正如预测般回落至飓风前新修复种植园中的检测水平。 定殖概率保持不变或有所提升的物种（如黄脸草雀（Yellow-faced Grassquit）、北方嘲鸫（Northern Mockingbird）、波多黎各食籽雀），其种群恢复的可能性更高。而食果动物如波多黎各牛雀，其定殖率从飓风前的0.56 ± 0.12降至飓风后的0.04 ± 0.20，无论处于何种修复阶段，其种群恢复都将十分漫长。 本研究表明，与修复后咖啡农场相关的鸟类群落表现出较强的生态抗性：飓风前后的物种组成相似度达81%，且12种焦点物种在两种修复阶段的农场中均持续存在。焦点物种的恢复前景存在物种特异性，在部分案例中还受其对特定农场修复阶段的偏好所调控。 据预测，随着全球变暖，飓风的强度将不断增强。未受破坏或受轻度破坏的遮阴种植园或完全修复咖啡种植园，可通过提升景观尺度的栖息地冗余助力物种恢复力，并为物种提供栖息地转移的契机，使其能够获取食物资源或依托源种群定殖受飓风破坏、正在恢复的栖息地片区。