Hi Ken and
to the forums!
I'm so glad you were able to rescue this little guy. I'm glad he made it long enough for you to rescue him!
It's good to hear that he's doing well so far. He probably loves the warmth and abundance of food!
Keep an eye on him and if he shows signs of lethargy, heavy breathing, or stops having an appetite, you should take him to an avian vet. If you don't have avian vets in your area, often "Exotics Vets" treat birds.
Since he's been outside by himself, I would recommend taking him in anyways to ensure that he's healthy.
As he recovers from the ordeal, put up posters and ads stating that you have found a budgie, but don't describe him. If someone has lost a budgie, they can call/email you and describe him to you, so you know people aren't trying to get a free bird.
If you don't find his owners, will you be keeping this little one?
Meanwhile, you've come to the very best place to learn even more about budgies. Be sure to read through all the articles and "stickies" (threads "stuck" to the top of each subforum for easy reference) to ensure you have all the right information to care for this little one. A roomy cage is a great start!
If you have any questions after reading through everything, please be sure to ask as we'd love to help
We'd love to meet him when you get a chance!