Bird survey of Budai salt pans in Taiwan

Study Extent

The sample plot included the seven main areas of the Budai salt pans (old area 5, area 6, area 7, area 8, area 9, area 10, and area P), consisting of a total of 51 salt pan sampling sites. Within the sample plot, area 6 and area 7 are currently listed as Important Wetlands in Taiwan by the Wetland Conservation Act. The area of every salt pan is between 3.4-48.4 ha. The total sample plot is about 1,030 ha. Significantly, the construction of solar photovoltaic facilities in area 8, following November 2018, resulted in a reduction of waterbird habitat areas.

Sampling

Monthly bird surveys were conducted between 2016 and 2022. Each survey lasted 1 to 2 days and employed the counting flocks method.

Quality Control

To maintain survey quality, several experienced investigators carried out the surveys. In January, 2016, and January and December, 2019, and January , 2020-2022 in accordance with the Taiwan New Year Bird Count, other volunteers took part in the survey. To reduce errors while documenting the recorded data, if the bird species was rarely observed or the quantity recorded was abnormal, we reconfirmed the details with the investigators. The classification system employed was the eBird Taxonomy v2022 (Clemnets et al. 2022), and the Chinese names of the birds were referenced from the Checklist of the Birds of Taiwan (Ding et al. 2023).

Method steps

1. We scanned each sample plot with a monocular telescope and recorded the bird species, abundance, and behavior (foraging/non-foraging). For this dataset, waterbirds were complete inspected in each survey; complete records of landbirds were only created for January-March, 2016 and January and December, 2019 and January, 2020-2022(see DwC event “samplingProtocol”). Waterbirds include shorebirds, waterfowls, wading birds (herons, egrets, storks, spoonbills and ibises), gulls, terns, cormorants, grebes, coots, moorhens and kingfishers. To understand whether the rise and fall of the tide influenced birds in salt pans, further surveys were conducted in 2017 –2020. Specifically, March - May and September - December in 2017, January – May and September – December in 2018, and January – March in 2019 and January-March, 2020. Five salt pans (10-01, 10-02W, 10-03W, 10-11, 10-12) were selected, and bird surveys were conducted during high tide and low tide of the same day (see DwC event “eventRemarks”). High tide was defined as three hours before and after high tide, low tide was three hours before and after low tide.

From 2016 to 2022, the survey recorded 135 species of aves from a total of 33 families. Within the records.

1. Ave
   common name: Bird rank: class

The study site of this project is Budai town, located in the southwestern coast of Taiwan (23°22'24.9"N to 23°18'39.1"N, 120°08'57.9"E to 120°11'23.4"E, Fig. 2). The Budai town is a land subsidence area (WRPI 2007), and the salt pans are below sea level (elevation -1.8 to -0.5 m, Kuo and Wang 2018). The temperature and rainfall data from 2010 to 2017 were obtained from the Chiayi weather station, located 30 km northeast of the sample plot; on average, the month with the lowest temperature is January (16.7 °C), the month with highest temperature is July (20.1 °C). The year with the lowest recorded rainfall was 2011 with a total of 1021.7 mm of rain; the year with highest recorded rainfall was 2013, with 2580.5 mm of rain. The Budai salt pans are brackish wetlands. According to the field investigation records of this study, the salinity was highest in May (30.9 ± 7.9 psu) and lowest in August (8.4 ± 2.0 psu).