Long-term monitoring data inform conservation strategies for waterbirds in the abandoned tropical salt pans of Budai, southwestern Taiwan

Abstract

Coastal salt pans are recognized as important habitats for waterbirds. However, once salt production ceases, the ecological management of these areas is often limited. Establishing long-term monitoring programs is essential for effectively informing conservation management plans. We conducted a monitoring program in the Budai salt pans, a critical wintering site for waterbirds in Taiwan, and analyzed survey data to assess population trends (2016–2023) of 30 species and waterbird abundance with environmental factors. A total of four dabbling duck species showed a significant decline, but no downward trend was observed at larger spatial scales, indicating that the salt pans may have become unsuitable for them. We recommend prioritizing dabbling ducks in the Budai salt pans as a conservation target. Water depth and salinity were the most important factors affecting waterbird abundance. Water depth was negatively correlated with the abundance of shorebirds and large wading birds. Dabbling ducks, as well as gulls and terns, significantly decreased when the average water depth was over 30 cm. In contrast, diving birds significantly decreased when the average water depth fell below 20 cm. Salinity had a negative effect on most guilds. Turbidity was negatively correlated with the abundance of diving birds. Tides affected small shorebirds, with higher abundance appearing during high tides. Creating varying water depths and reducing salinity are general management measures that contribute to waterbird conservation in salt pans.