Mice/Keeping or releasing orphan field mice
My sister rescued two baby mice from her cat. When found, they still had their eyes closed. She followed your directions for feeding and caring for them. Now their eyes are opened and eating kitten formula from a saucer, and she wants to know what will be a good food to start off with and when should they be released back into the wild? Her parents will not allow her to keep wild mice as pets.
She can start off by just putting a number of food items in the cage and letting them choose. She should give them some vegetables and fruit, some crackers, a bit of cheese, etc. If she is going to feed them mouse seed, she should put that in right away. They will start eating these things pretty quickly.
It is a real pity to release hand raised wild mice in the wild. Hand raised wild mice make wonderful pets. They live longer and are very loyal. And they are much smarter than a pet mouse.
If her parents just feel that as a philosophy, wild animals should not be in captivity, let me explain how I feel, and you can explain it to them as gently or candily as you like. The philosophy that wild animals should never be pets, is based on nothing reasonable; it is silly. If something "should" then there must be someone to whom it matters. But unless they have a strong belief that God will be angry, there is no one to have to answer to. Nature doesn't care. In fact, Nature has created these little beings to be extremely flexible and adaptive, and live in any environment.
The only thing that matters is happiness, and the best thing for the mouse. A mouse raised in the wild will hate a cage, and so it shouldn't be in one. A mouse raised by hand wants to stay a pet with the person it loves. That's all that matters, in my opinion. If it would be acceptable to keep a pet store or bred mouse as a pet, it should be OK to keep these guys. It is the thing which will make both your sister and the mice happy.
But maybe even this will not sway her parents. If you know of no one who wants some sweet little hand raised mice as pets, she will have to let them go. Wait until they are about 5-6 weeks old. Wikipedia tells me they won't mate until they are 50 days old, but I would still separate them at 5 weeks to be sure, whether she is going to keep them or not-- she doesn't want to release a pregnant mouse in the wild where it has to immediately deal with the emergency of babies. Wild field mouse bucks can actually live together much of the time; so there need only be two cages. Or she can release the bucks (males) and keep the does (females).
There is a pet wild mouse "ranch" in Colorado (as far as I remember) if she is near there! They take in hand raised orphans. She should check out their site.
I just found this thread about keeping a wild orphan. It is interesting.
Best of luck and I hope her parents let her keep them!
Squeaks n giggles,