I agree with lady. Only time I have had a truly unexpected chick death was due to suffocation from the other chicks or pine shavings being eaten. Pine shaving-related death we usually saw pine shavings in the beak, swollen crop. Now we put paper towel over the pine for a week to prevent shavings being eaten. For suffocation, it was more difficult to tell. There were zero signs of anything we could see. I'm a crazy chicken lady, so I found someone to do an autopsy on my chick. I was concerned about diseases. Came back clean, and the vet tech said she looked "crushed on the inside". We now use a big heat plate that sits on the floor inside the brooder. This heats the chicks from underneath instead of from above like a normal heat plate, so they don't pile up on each other. They learn very quickly that laying all spread out keeps them warm. In colder states, I don't know if this kind of heat plate would be enough for young chicks. We live in Florida, and keep our babies in the garage which stays hotter than the rest of the house anyway. If it's below 65, we move them to a cardboard box with a heating pad on high under the box and the heat plate with a blanket over half the box. The heat plate and pad only cover half the box so they have space to move if they get too hot.