Data from: Assessing the effects of human activities on the foraging opportunities of migratory shorebirds in Austral high-latitude bays

Human presence at intertidal areas could impact coastal biodiversity, including migratory waterbird species and the ecosystem services they provide. Assessing this impact is therefore essential to develop management measures compatible with migratory processes and associated biodiversity. Here, we assess the effects of human presence on the foraging opportunities of Hudsonian godwits (Limosa haemastica, a trans-hemispheric migratory shorebird) during their non-breeding season on Chiloé Island, southern Chile. We compared bird density and time spent foraging in two similar bays with contrasting disturbance levels: human presence (mostly seaweed harvesters accompanied by dogs) was on average 0.9±0.4 people per 10 ha in the disturbed bay, whereas it was negligible (95% days absent) in the non-disturbed bay. Although overall abundances were similar between bays, godwit density was higher in the non-disturbed bay throughout the low tide period. Both days after the start of the non-breeding season and tidal height significantly affected godwit density, with different effects in either bay. Time spent foraging was significantly higher in the non-disturbed bay (86.5±1.1%) than in the disturbed one (81.3±1.4%). As expected, godwit density significantly decreased with the number of people and accompanying dogs in the disturbed bay. Our results indicate that even a low density of people and dogs can significantly reduce the foraging opportunities of shorebirds. These constraints, coupled with additional flushing costs, may negatively affect godwits' pre-migratory fattening. Hence, as a first step we suggest limiting human presence within bays on Chiloé to 1 person per 10 ha and banning the presence of accompanying dogs in sensitive conservation areas.

人类在潮间带（intertidal areas）的活动可能会对沿海生物多样性（coastal biodiversity）造成影响，包括迁徙水鸟（migratory waterbird）物种及其所提供的生态系统服务（ecosystem services）。因此，评估此类影响对于制定与迁徙过程及相关生物多样性兼容的管理措施至关重要。本研究针对智利南部奇洛埃岛（Chiloé Island）非繁殖季的棕塍鹬（Hudsonian godwits, Limosa haemastica，跨半球迁徙滨鸟（trans-hemispheric migratory shorebird）），评估人类活动对其觅食机会的影响。我们在两个环境相似但干扰水平截然不同的海湾中，对比了鸟类密度与觅食耗时：受干扰海湾内的人类活动多为携带犬只的海藻采集者（seaweed harvesters），其平均密度为每10公顷0.9±0.4人；而未受干扰海湾内人类活动可忽略不计（95%的天数无人类活动）。尽管两个海湾的鸟类总丰度相近，但在整个低潮（low tide）时段，未受干扰海湾内的棕塍鹬密度更高。非繁殖季开始后的天数与潮高（tidal height）均会显著影响棕塍鹬密度，且两个海湾的影响模式存在差异。未受干扰海湾内的觅食耗时占比显著更高（86.5±1.1%），受干扰海湾则为81.3±1.4%。正如预期，受干扰海湾内的棕塍鹬密度会随人类及随行犬只数量的增加而显著下降。本研究结果表明，即便人类与犬只的密度较低，也会显著降低滨鸟的觅食机会。这类限制因素加上额外的惊飞成本（flushing costs），可能会对棕塍鹬的迁徙前脂肪储备（pre-migratory fattening）产生负面影响。因此，作为第一步措施，我们建议将奇洛埃岛海湾内的人类活动限制为每10公顷不超过1人，并在敏感保育区域内禁止随行犬只进入。