need a crash course in geese.
Here are a few things to consider to start:
First and foremost, geese are large birds. They require significantly more living space than chickens, and while they can eat some of the feeds provided to chickens, you have to watch the protein levels. Too much protein may cause the geese to develop "twisted wings" where the wing feathers stick out at odd angles (the same phenomenon is seen in ducks).
As a large member of the waterfowl family, geese shouldn't be housed with chickens in the same enclosure/pen. Geese can get sloppy with their water and turn things pretty muddy, and that makes it really difficult to keep chickens happy and healthy. I recommend giving geese ample water to swim in, even if it's just a kiddy pool, in order for them to keep cleaner and happier.
Additionally, keep in mind that unless you're buying goslings, adult geese may take a long, long time to tame down. The goslings I used to take to the fair were the only ones in the entire flock (12-15 birds total) that tolerated people exceptionally well. The rest of the flock would move to the opposite end of the pen away from me.
Most geese are not overly aggressive toward people, but they can become aggressive when the goose (hen) is laying or on the nest. Broody chicken hens may pick a little at you, but a goose's powerful wings can deliver a nasty hit. I have never been bitten or attacked by a goose (10+ years of poultry experience speaking here), but it's important to be mindful of the damage that can be done if you're not watchful.
Geese can be rewarding birds to keep, but they can be challenging for a beginner with limited goose experience. Be sure to do your research!
Geese eat primarily grass, supplemented with grit and waterfowl food, lots of members here can tell you what they use.
You're better off buying a couple goslings from a hatchery this spring and raising them by hand, geese can be nasty if they're not trained, and even then breeding season is normally a mess.
You will need to build a house for them, never leave waterfowl outside at night, especially geese because they are pretty slow compared to ducks and chickens, and they don't fly well if at all.
Geese don't *need* water like ducks do for swimming but they will be very happy with a small kiddie pool to play in, and they must have fresh water deep enough to put their whole head in at all times so they can clean their nares (nostrils) and their eyes. They also must have water with their feed because they can choke if it's too dry.
I suggest you read as many threads as you can, learn as much as you can. You'll love having geese and I think you may like them more than your chickens!
- Plum Nearly Farm
And you can have geese without grass but like it has been said you'll have to supplement them with fresh greens every day.