I think it would be great fun!! It's always easiest to begin with a behavior that they do naturally (pecking,say) and teach them to do it on a cue.
Method: wait for chicken to peck. SIMULTANEOUSLY with the peck, click the clicker. Then give a treat. Timing is vital as it is the click that marks the behavior that you are rewarding for, so if you are slow you may be marking looking up after pecking as desirable, instead of the peck. Many people say to first "charge" the clicker by just clicking and following quickly with a treat - I think they figure that part out pretty quick, and if you just start clicking for stuff you want them to do, they begin to offer different behaviors to see what will make you click that thing, which is a riot.
After they have begun to reliably peck when they know it's a training session, start saying "peck" at the same time they do it. Gradually precede the behavior with the cue ("peck!") and pretty soon you'll find that saying "peck" nets you pecking, expectant chickens.
There's lots more to it, but that's the basics in a nutshell. Search for "operant conditioning" "clicker training" "positive motivational training" or, believe it or not, "chicken clicker training". There's a dog trainer out there teaching other dog trainers to use the clicker with chickens, as he says they are so quick it's the best way to perfect you timing with the tool. My personal bible for this method is Karen Pryor's book, "Don't Shoot The Dog".
Training is more effective in frequent, short sessions than longer ones. Five minutes as many times a day as you care to trot out there with treats is fine. And make sure they are either A.fairly hungry or B.your treat is very high value for them.
Please post and let everyone know how you are doing!
Two of my chicks at three weeks old will hop onto my outstretched hand on "Up!". I probably could train any of the 11 by separating them, but working with anyone who will come over for a session I think netted me the most motivated chickens. It's amazing what it's done - both of them are less afraid of me, happier about being picked up, enjoy being petted more - and are tending to hang around together now. Interesting.
Have fun.
