Dunlin with leg bands

Scientists attach uniquely numbered metal bands to birds leg to identify them. Banding studies in North America are regulated by the USFWS and banding data is managed by the USGS. Studies that need to identify individuals from year to year do this by placing colored bands and field-readable flags on birds legs. Each individual from a study can be identified by their unique combination of colors and the alpha-numeric code on the flag. Furthermore, the flag colors for shorebirds are coordinated among countries. Birds banded in North America are banded with green flags, like the Dunlin pictured here.