Just got delivery of 15 3 day old Barred Rocks. They all seem happy and have moved into the makeshift brooder (a kiddie pool with pine shavings). Heat doesn't seem to be a problem as they are circulating to and from the heat lamp and eating just fine. The question is... why do the keep pecking at the side of the pool? It's constant, sounds like rain on a plastic corrugated roof! Is this normal?