WHISTLING SWANS DYED TO STUDY MIGRATION ROUTE — The U.S. Fish and Wildlife Service has been dyeing whistling swans vivid colors to learn more about their migratory movements. With their wings, tails or other body parts colored blue, yellow, green or red, the swans are easier to observe both when flying and resting on the ground. The Service is interested in determining over which states the birds fly in their annual migrations…. Actually only a very small sampling of the whistling swan population is being dyed. This is because of the difficulty in trapping the four-foot-long birds. Mass dyeing, however, is not considered necessary. The dyes used normally do not remain on the swans for very long.