Have you ever tried to get a really good shot of a bird? No? Good. Don't EVER try. Fate, and birds, are fucking cruel. On your first attempt at photos, you will get precisely one that is almost perfect. The bird will sit still, pose dramatically, Apollo will shine upon your impromptu stage like a nuclear-powered Care Bear, and the only problem will be your focus having been slightly off.
Every other time you go out from that point on forever, no birds will cooperate. I've heard stories of photogs who wear wetsuits to slither through the mud without making too much noise, just so they can get within 100 feet of a bird before it flips out and flies to Capistrano. It's insane. My recommendation is to simply shoot the birds. Like, with a gun. Then simply walk up and photograph them on the ground. It's much easier.
But if you absolutely have to photograph them, I have some recommendations. One: seed. Unless you are the most patient person in the world, seeking out the birds is 100% pointless. Set out traps of seeds, flowers, and anything else you can manage that will attract birds. With this, your own back yard can be one hell of a studio. This is doubly helpful since you'll only ever want to shoot in sunlight. At the focal lengths you will need, shutter speeds below 1/800 are useless.
And this is a big one that has paid huge dividends. Set your stage, be it flowers, a bird feeder, a tree with peanut butter and seed, whatever. Frame your shot. Connect to your camera via a WiFi memory card. Use an RF remote shutter. Then take photos from WAY far away. Likewise, if you have time, you can set up a full blind with a two-way mirror. I have never gone so far as to do that, but I'm seriously contemplating it for the next few months.
Birds are bitches.