What lenses do you have? Birding is one of the most demanding photographic activities, it puts a lot of stress on the lens. The longer/better the lens, the happier you'll be Do you have an idea of the type of birds you'll encounter? For tame wild birds a 70-200 should give you good pics, but for timid birds the longer the lens the better
I should have specified, I only have the 18-55mm lens. I hear that some of the birds will actually land on people or come up close to be fed, so I'm hoping I won't need as much zoom as a telephoto lens would provide.
Then the 18-55 will be just fine Be sure to take seeds/bread crumbs/bird food then. For settings, I'd avoid the lens wide open, as the edges are a bit soft. This may mean raising the ISO for a decent shutter speed. Experiment as much as you can! Try to get a shot of your gf with a bird eating out of her hand. She has to stand/sit very still with bird food in her open palm, but they will eventually come if they're as tame as you say they are. Keep an eye out for good landscapes And (this is just a quirk of mine) I always try to shoot animals in their natural surroundings. So don't be afraid to include some trees/bushes. Spare batteries and extra memory cards are always good, and you might consider a light tripod
EDIT: Some birds I've seen at a mountain nearby are so "trained" that they'll snatch a piece of bread in mid air if you toss it up. You might try it for a shot of a bird in flight! Those are always cool, if the shutter speed is high enough to freeze the wings