Learn the system
Learn one character at a time—middle code, plumage, cycle, and then the current adjunct codes—with immediate feedback.
Begin the tutorial →WRP is a universal system for categorizing age using predictable molt and plumage patterns shared by birds worldwide. It replaces calendar-year-based categorization systems while retaining more biological information, remaining flexible across species, and avoiding seasonal constraints. The tools used to determine age—including skulling, gape, feather wear, and other species-specific criteria—remain unchanged.
Calendar-year systems can separate cohorts when breeding is strongly seasonal, but become difficult to apply when breeding overlaps January 1—as it commonly does in tropical regions, the Southern Hemisphere, and among irregular breeders. Introduced in 2010 and refined through subsequent research, WRP instead asks where a bird is in its progression through molts and plumages. That biological foundation allows the system to work across species, latitudes, and breeding seasons.
Follow the guided lessons from the beginning, jump directly into photographic practice, or use the site as a reference library.
Learn one character at a time—middle code, plumage, cycle, and then the current adjunct codes—with immediate feedback.
Begin the tutorial →Already know WRP? Assign complete codes to real birds, reveal molt limits, and work from foundational to advanced cases.
Open practice →Watch the tutorial, consult the current code table, and read the foundational papers and subsequent updates.
View resources →