In the city, your neighbors can be more of a hassle than wildlife. Chickens will wonder farther than you think, specially if someone across the street just laid beautiful black mulch for them to dust bathe in. Growing up I had free range birds, we were the last house on a dead end street with a field next door and woods beyond that. But there the chickens went, across the street instead. The people living behind my dad's house now, on a busier road, across from the golf course, also have chickens now. They've been known to follow my dad's fence all the way around to his porch. No chickens live with him anymore, the neighbor birds just wondered that far. Or they'll fly over the other neighbor's 4 ft chainlink to get to his grass. Or they'll be in the road. Not good!
If your yard isn't fenced in totally, or if your birds routinely fly over your fence, you'll need to find a way to contain them. City chicken free range works best if you set out there with them over your coffee to be able to steer them back where they belong. The complaints that come along with wondering birds in people's yards will be a hassle that may end up in you having to give up the birds. The way my ordinance reads, I can have them as long as no one complains. So mine have an 8x10 storage building to live in (blends in with the suburban scenery) and an 8x10 run, with supervised free range. So far they haven't tried to fly over the fence. The stray cats have been known to watch from the neighbor's brush pile. The cats know dogs live here, and perhaps they're worried the dogs will come out if they cross the fence. We did have a hawk crash into the roof on the run, surprising, since I thought hawks had pretty good vision and the run is topped with visible fencing.
Raccoons haven't tried for them, I don't think they have a taste for chicken. I have seen them in the trees eating nuts above the coop... good for them. Squirrels are fascinated, they'll sit low and watch the chickens. Chickens are fed inside their house, with all windows of the coop covered in rabbit wire, so that the wild birds don't learn how much food is in there. They could go through the roof wire and through the pop door, but they don't seem smart enough to figure that out yet. I was worried some migratory birds might have known about chicken coops and the food, but so far so good.
You can clip the wings for shorter perimeter fencing. But you definitely want a secure run as chicken "base camp" for when you can't watch them. They'll still have safety and access to the outdoors, without causing trouble or getting into trouble while you're gone. Or a self contained chicken tractor you can move around the yard. I opted for stationary so I could have a bigger living space for them.
