Abstract Grazing pressure by animals can change the distribution and biomass of seagrass. We examined grazing pressure by conducting transect surveys and acquiring aerial images by drone before and after the arrival of migratory birds along the Asadokoro tide flats, Aomori Prefecture, Japan. The distribution and biomass of the seagrass Zostera japonica decreased sharply between October and November 2018, which was when migrating waterfowl arrived. We hypothesized that grazing pressure by migrating birds such as the Anatidae, including whooper swans (Cygnus cygnus) and brent geese (Branta bernicla), had a major effect on the decline in Z. japonica in late October. Shortly after the Anatidae arrived, most of the Z. japonica in the shallows disappeared, including the belowground parts. The abundance of Z. japonica in this area was insufficient to support wintering swans. Swans likely need food other than Z. japonica for overwintering.

中文翻译：

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候鸟对海草Zostera japonica分布的影响

摘要 动物的放牧压力会改变海草的分布和生物量。我们通过在候鸟沿着日本青森县 Asadokoro 潮滩抵达前后进行横断面调查和使用无人机获取航拍图像来检查放牧压力。2018 年 10 月至 2018 年 11 月，正是迁徙水禽的到来之际，海草 Zostera japonica 的分布和生物量急剧下降。我们假设迁徙鸟类（例如鸭科）（包括大天鹅 (Cygnus cygnus) 和布伦特鹅 (Branta bernicla)）的放牧压力对 10 月下旬 Z. japonica 的数量下降产生了重大影响。鸭科到达后不久，浅滩中的大部分粳稻消失了，包括地下部分。丰富的Z。该地区的粳稻不足以养活越冬的天鹅。天鹅可能需要除 Z. japonica 以外的食物来越冬。