Ageing & Sexing Techniques & Terminology

Age categorization in North America is classified using the calendar year because most species adhere to specific breeding seasons typically occurring in the spring and summer.

Things get more complicated for tropical landbirds with variable nesting seasonality and a new cycle based system to categorize bird age based on molt and plumage cycles has been developed. Called Wolfe, Ryder Pyle or the WRP system.

The following slides provide a full explanation of the WRP codes and how they are used in conjunction with the alpha age codes generally used in North America.

At this time VARC continues to use the calendar year age categorization codes with those explanatory timelines provided below.