What is the exposition of the wringer?

In the exposition of "Wringer" by Jerry Spinelli, we are introduced to the main character, Palmer, and his fear of becoming a "wringer" - a role in his town's annual Pigeon Day event where boys wring the necks of pigeons. We learn about the community's tradition of pigeon shooting and Palmer's internal conflict as he approaches his tenth birthday and the possibility of being forced to participate.