I am in Middle Smithfield also. You can check the zoning at ecode360. What I gather is you can have up to 5 pets commonly sold at a pet store. Poultry falls under agriculture. For that you need 2 acres. There is some way to get an exemption thew the Monroe County Conservation District. I spoke to one of the township reps and she seemed positive about backyard chickens. Our neighbor Smithfield was in the paper a couple of years back, and the poor guy was given 15 days to dump his chickens, and $500 fine per day after if he didn't conform.
At ecode there is mention of exemptions:
The Agriculture, Communities and Rural Environment Initiative (ACRE), amending Title 3 (Agriculture), also provides additional exemptions from municipal zoning regulations. [Note: See 3 P.S. § 1717, 3 P.S. § 911(b), 3 P.S. § 951 et seq., 53 P.S. § 10603(b), 53 P.S. § 10603(h) and Act 38 of 2005, respectively.]
But I have not had the time to dig further. The borough allows up to 25 chickens, but I don't remember seeing anything about property size. NYC 5 boroughs have no limit on the number of chickens or minimum lots.
They all have zoning in place for structures, odor, noise etc.
Maybe we fix this.
D