Capture methods and sampling
Dunlin individuals were captured during the autumn migration period in 2015 (12–20 September) and 2016 (26 September to 6 October). Birds were captured on intertidal flats and adjacent lagoons behind the sea wall where they roosted at high tide in different ways, depending on time of day, weather conditions, and stage of the tidal cycle. Canon nets and elastic-powered whoosh nets were used to trap birds in daylight, whereas mist nets and dazzling with lights were used at night. A total of 791 dunlin individuals were captured. Birds were placed in keeping cages before being processed. Birds were banded with a metal band and color flag (upper green and lower blue). Maximum chord wing length was measured to the nearest 1.0 mm with a wing rule, and bill and total head lengths were measured to the nearest 0.1 mm with dial calipers. Blood samples, 20–50 μL, were collected from some individuals by venipuncture from the wing vein and stored in 0.001 M Ethylene Diamine Tetraacetic Acid (EDTA). Cotton swabs were used in beaks to collect epithelial cells, and coverts from the belly were also collected. All specimens were stored in 75% ethanol and immediately placed into an icebox.