I know a LOT of people who live in the city who would LOVE for the city to allow them to have backyard chickens, with that said I imagine not all people appreciate the benefits of chicken poop, especially if they are roosting in a tree over their yard. I think your best bet is to get a fence because if the city gets too many complaints they just might revoke the backyard chicken thing. If it's flying that high to roost in a tree some wing clipping might be in order also, nothing worse then making enemies out of neighbors and they can get pretty revengeful.
Thankfully I live on the edge of a small country town and one of my neighbors who is IN city limits is allowed to have backyard chickens just no roosters. Part of my property is in city limits (oddly enough it's the "forrest" part of my property) and then where the house and everything else and part of the "forrest" is out of city limits so they can't really dictate what I can or can't do as if they don't like it I just step over to the "out of city limits" part.
Thankfully I live on the edge of a small country town and one of my neighbors who is IN city limits is allowed to have backyard chickens just no roosters. Part of my property is in city limits (oddly enough it's the "forrest" part of my property) and then where the house and everything else and part of the "forrest" is out of city limits so they can't really dictate what I can or can't do as if they don't like it I just step over to the "out of city limits" part.