When I give my chickens something new I make sure it's small like bite size for chickens and hand feed them a small amount. Later I bring the rest of the new item to them, they usually nibble at it throughout the day.
But they definitely have there own favorites.
The first time with melons I showed them how to pick it out with my fingers and gave them the small piece I picked out. After that they just pecked at it and ate it on there own. I give them cantaloupe, watermelon, and honey dew in the summer only.