Originally Answered: Outdoor kitty now an indoor kitty?
In a way -- and this is not a nasty response -- your cat is answering your question, and because cats are all different, he really is the best one to answer it. If he is frisky and has located his tail as a replacement for butterflies and leaves, is eating even better, he likes being indoors.
You may want to go to the pet supply store -- or go online through some catalogues -- (www.drsfostersmith.com) and get him a window seat. They are fleece-covered little (1.5' x 8") platforms that hook over a ridge of the window sill and have a little foot that braces against the wall and holds the seat verticle. Cats sit on them and look out the window. Just leave the window open only a little so he can sniff the breeze, and then he can participate in the outdoors without actually being outside. Put the seat in a window that has some action outside -- human comings and goings or treetops with birds -- if possible, but any window will do. Here in NYC, my cat watched helicopters. Some of them are as much as $50; some as low as $10.
Get him some toys. There are some wonderful catnip cigars -- the perfect thing for a male cat -- by El Gato Muy Loco. The quality of the catnip is out of this world.
There is a wonderful toy (available at K-Mart for $12 or so) the Turbo-cat scratcher, in which the center is one of those corrugated scratchers into which you rub catnip (supplied) and the outer part is a ball in a circular track. Cats loll and drool on the scratcher, and then they discover the little ball in the track, and they start to bat it around and attack it. It can provide you interactive play with the cat, but he can also hunt the ball and bat it around the track without your help.
Most pet supply stores have a toy called "The Cat Dancer". There are two models of it, the $4-5 one or the $6-7 one. You want the more expensive, because it mounts to the wall (not well, and you will have to find a way to reinforce it). This toy sounds like it's not worth the money -- an in terms of materials, it isn't. But in terms of cat joy, it is priceless. It is a little, rolled piece of rock hard paper on the end of a very turgid, bouncy wire. You attach one end of the wire to the wall, and that little, rolled piece of paper bounces and flies just like one of the insects he used to chase when he was outside. He will leap for it and bound around -- but only right there in the place you hang it -- and really get his exercise. And he will forget his tail.
Finally, there are some wonderful feathers on sticks, very brightly colored, and sometimes with some mylar strips in the center. These make great interactive play with your cat, and if you flap them just right, you can make them sound and look just like a bird taking off, which will permit him to do some hunting right in your living room.
I'm sure other people will have other suggestions, but I think these items will wean your happy little camper off his tail, and give him that outdoor experience, in a much safer, already very loving, environment. Good luck, my dear.