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. The number of eggs it lays in relation to other birds of the same breed can give you a clue. 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 few years old, whereas if it lays 5-6 eggs a week, it is probably only 1-2 years old. The condition of the vent is also an indicator: a moist, pink-looking vent indicates a younger bird.