This ingenious 8” calculator wheel accurately tells landlords five important things about each active nest under their care: 1) the clutch-initiation date of each nest, 2) the hatching dates of eggs in each nest, 3) the age of young on any given date, 4) the earliest possible fledging dates for the young in any nest. Based on these dates, landlords can determine: 5) the breeding success of each nest (i.e., whether young have fledged successfully from a nest, or disappeared prematurely due to predation or other causes). To operate, simply place the number of eggs in a complete clutch (from the inner wheel), opposite the date (on the outer wheel) when the first egg in that clutch was laid. Read around the wheel to predict hatching and fledging dates, and for nestling ages on any given date. The back side of the wheel has detailed instructions on how operate the wheel. Made of weatherproof plastic.