My sister is an avid bird watcher and an avid cat person.
she was not going to give up either one. So the cat get full run of her house but only gets to go outside with a harness and leash he does sit at the window and is fascinated with the birds just outside. the first few years he snuck out a few times but he is 7 years old now neutered and less active but would still hunt if he got a chance.

Keeping cat indoor is the best for your cat and for the animals on your yard. But if this is not possible, you can try using a catbib.

Here is a link that might be useful: Catbib

my next door neighbor has a loud bell on her cats collar and it's a help but the cat is not a hunter anyway and mostly sits and stares at the birds and makes a long run across the yard and the birds are already gone before it get close

OH dear. This is a very hot topic here. You may get some "not so nice" comments. First off I love cats, I have 4. They were brought in as strays and they have never set foot outside since (except my Ernie who likes to run out the door in the spring, I grab and bring right back in). Cats are killers of native wildlife as you have seen. There are many reports of the damage cats do to wildlife including birds. I am sure someone will send you links. There are also ways to let your cat enjoy the outdoors without puting your birds and critters at risk and I am sure you will get those links too. Please consider the safety of you cat and the safety of the critters and keep the cat inside unless you are with it. One other thought, and I am fighting with this now, your neighbors may not be any too happy with your cat in their yard. My neighbors let their cat out. First, I am a certified wildlife habitat with 5 nestboxes and 5 feeders, I have the right to not have the neighbors cat killing my critters including the frogs and toads in my pond, the cat does not belong on my property. Second the cat pees and poops in my garden. I should not have to put up with this , it's MY property. As you can tell I'm quite angry about this. Also I worry that any day I am going to see that cat dead in the road, I like the cat and would be extremly upset. Please reconsider letting your cat roam. It's not safe for the cat, your critters or birds and your neighbors will be happier. Hopefully someone can send you the link to the cat outside enclosures (I think Starlinka has one). Bells don't really work as birds do not know bells as being a threat until they have been attacked. Bless you for taking the cat in , now please keep it and the critters safe.

Like I keep saying, the coyotes around here keep the stray cat population at bay.

Fledgling song birds spend a few days near the ground and are easy prey to domestic cats, along with unwary adults.

If a cat even scratches a bird, it can get blood poisoning, and cats are the only species to shed the dangerous Toxoplasma gondii parasites in their feces, which stay alive for outside for months and cause severe illness in infants and people with weakened immune systems

http://www.tnrrealitycheck.com/barn_cats.asp

Strangely, like some Star Trek episode, scientists have recently found that the dangerous Toxoplasma gondii parasites carried by cats force rats to seek out cats so they can be caught, the parasites can infect the cats, and they can complete their cycle

http://www.npr.org/templates/story/story.php?storyId=9560048

Yes, I forgot to mention - an outdoor enclosure is great for letting your cat enjoy the out doors and it keeps him and the birds safe.

Im planning on one of these for Ernie this year!

I am in agreement with everyone else. It's best to keep the cat inside. They are not natural predators of our native songbirds, and they can cause quite a lot of death. I am not a cat owner, and I do not dislike cats unless they come into my yard to prey upon my songbirds. It's like a baited hunt, and it really is so unfair to the songbirds and to me. Sounds like you really love your kitty, and that is a wonderful thing. :o)