Yes, that's right. This boy baby budgie is very young. The further down the stripes are, the younger he is. It looks like he's 3-4 months, although some lines of budgies lose their stripes slower than others. Mine lose theirs very slowly for some reason. I guess they stay young at heart forever

I'm very worried about his digestive system, however. Usually, any discoloration (usually brownish-green) near the vent area (butt, basically) can signify a liver problem. Liver problems are prevalent in seed-only budgies which this baby probably is. You might want to check him in with a vet if the shelter won't take him in or you're his official foster.

Also, what type of seed is he getting? Wild bird seed isn't very nutritious for budgies, so you might want to head out to the pet store and buy some pellets (Lafeber, Zupreem, Harrisons, KayTee) and pulverize it into a powder. Hehe....Methinks you should keep him You're sure to be a greyt mommy and we'll always be here to help you.

P.S. Due to his young age, be sure the room is moderately warm (70*F is about right). Good Luck and don't hesitate to keep him!