What stories do feathers tell? Every feather on a bird’s body serves an essential, life-sustaining purpose, like enabling flight, providing insulation, or attracting mates. Birds replace feathers through molting. Breeding, migration, and molting are the most crucial and energy-intensive parts of their life cycle, so they can only do one at a time. To learn more about these complex activities, birds in Glacier are caught as part of the MAPS program – Monitoring Avian Productivity and Survivorship