Danielle Kaschube of The Institute for Bird Populations explains the concept of the Wolfe-Ryder-Pyle system, starting with the original Humphrey-Parkes terminology, moving through the introduction of the plumage-based ageing systems to the system as it is today. And, then it presents some examples of how you would apply the system in the field using the Monitoring Avian Productivity and Survivorship (MAPS) protocols and coding.