First you need to read the rules of construction for your zon ing ordinance. MANY cities have a statement that says that unless a use is specifically allowed, it is NOT allowed. If that clase isn't there, and there are no other ordinances pertaining to animals that would place limits, then they are allowed. Period. Getting a writtten ordinance to allow a specified number of birds and placing restrictions would actually TAKE AWAY current rights. Not something I would subscribe to.