[header] How to repel chickens [title] Spray the chickens with water. [step] When you see chickens wander into your garden, give them a quick spray with a standard garden hose. Keep the water pressure light so that it scares the chickens without hurting them. 
[substeps] The chickens will usually return shortly after you spray them the first time, but if you do this consistently enough, they may eventually associate your yard with the water and start to avoid it. Since spraying them with a garden hose requires you to actually be present when the chickens invade your yard, you may not catch them all the time.