Seems like a good ordinance to me.
In my neighborhood many of the touchier points of chicken keeping, are left too much to the imagination. So if you have easygoing neighbors you can keep roosters, or have 25 meat birds, but if you have a complaining neighbor, like one of mine, you are given a hard time for keeping a few bantam hens.
I like the way in Durham the ground rules are specificly spelled out. It seems much more fair.
Good on you Durham, NC.