18S rDNA amplicon sequences for negative control 18S_Neg22
We collected fecal samples in the wetland in Mai Po Inner Deep Bay Ramsar Site (Mai Po). Shorebirds migrated to Mai Po were captured by mist net during 8-11pm between January 2019 and September 2020. Each bird was identified to species by morphology. To avoid cross-contamination from multiple shorebird species, only one or several individuals of the same species were temporarily kept in one breathable container for defecations. Each fresh fecal sample was collected inside the containers using a sterilized disposable spatula. In this study, we have collected 191 fecal samples from 22 shorebird species in 13 genera. Each sample was preserved in absolute ethanol in the field and stored at -80C on the same day until DNA extraction. The QIAamp Fast DNA Stool Mini Kit (Qiagen, Hilden, Germany) was used to extract the fecal DNA. We included mock communities and negative controls during DNA extraction in our analyses. We used a universal genetic marker (18s_SSU3_F: 5'GGTCTGTGATGCCCTTAGATG3' and 18s_SSU3_R: 5'GGTGTGTACAAAGGGCAGGG3') that amplifies the V7 region of 18S small subunit of nuclear ribosomal DNA (rDNA; ca.170 bp). We also used another COI marker specific to macroinvertebrates (COI_Ill_B_F: 5'CCIGAYATRGCITTYCCICG3' and COI_Ill_C_R: 5'GGIGGRTAIACIGTTCAICC3') that targets the Folmer region of mitochondrial cytochrome c oxidase I (COI; ca. 86 bp). All fecal DNA samples, mock communities, and negative controls were used for library preparation using 18S and COI markers through a two-step polymerase chain reaction.