I bought hens somewhere else and I want to know how old they are. How can I tell?
It is very difficult to discern the age of an adult chicken; the best you can do is make an educated guess. There are a few clues you might look for.
1. The number of eggs they lay in relation to other birds of the same breed. For example, if you have a Rhode Island Red that only lays one egg a week, there's a pretty good chance it's a several years old, whereas if it lays 5-6 eggs a week, it is probably only 1-2 years old.
2. The size of the eggs: young layers tend to lay extra small eggs. As a bird matures, its eggs get larger and larger. (A five year-old bird will lay eggs far too large to fit in a standard egg carton!)
3. The condition of the vent: a moist, pink-looking vent indicates a younger bird.
4. The condition of the shanks: (a chicken's lower legs) can clue you in: older birds have larger, rougher shanks, whereas a younger bird will have smooth shanks with a bit of sheen to them.
5. The molt: a hen under one year of age will not molt.