Layman's version:
Any chickens must be "kept securely enclosed in a yard or pen at all times."
 The Urban Chicken ordinance on the books:
Link to code online: Municipal code 6.08.010
Chapter 6.08 FOWL
6.08.010 Keeping prohibited—Exception.
It is unlawful for any person to keep or have under their care, custody or control, either as owner or otherwise, any chickens, ducks, geese, or poultry or fowl of any kind whatsoever, within the city, unless same are kept securely enclosed in a yard or pen at all times. (Prior code § 9.02.010)