Stable isotope, morphometric, and wintering ground assignment Data for Sanderling Migrating through Chaplin Lake, Saskatchewan (2012-2020)

This dataset contains stable isotope and morphometric data collected from 688 individual Sanderling (_Calidris alba_) captured between 2012 and 2020 at a key migratory staging site in Chaplin Lake, Saskatchewan, and at known overwintering grounds in Texas (USA), Peru, and Chile. This study was developed to investigate population structure and migratory connectivity using isotopic profiling of feathers. Data include feather isotope measurements (d2H, d13C, d15N), morphometrics (wing, bill, tarsus length, and body mass), age classification, and sex (where available). We provide two files. `chaplin_sand.csv` documents 567 birds captured at Chaplin Lake during northward migration. These birds were isotopically assigned to wintering regions (Chile, Peru, Gulf of Mexico) using linear discriminant analysis (LDA) informed by a 75% probability threshold, and clustered into five isotopic groups based on feather stable isotopes. The second file, `winter_sand.csv`, contains data from 121 Sanderling sampled at their overwintering sites in North and South America, providing the reference dataset for geographic assignment. This dataset provides a valuable resource for researchers studying migratory connectivity, population structure, and the ecological implications of non-breeding distributions in shorebirds.