How do stop pile ups

The light bulb is a good idea. They are piling for warmth - so make it warm in the coop. Then they'll spread out. At only 4 weeks, they still need it pretty warm - 75 degrees or so.

 

Are you monitoring the temp in their brooder? If so, what is it?

 

All of mine are 6 weeks old now and still aren't fully feathered. They still have down in some places from which they'll lose body heat, such as their butts and under their wings. The coolest temps my chicks experience is about 68ºF and while they do sleep next to each other, they're not piling up. I discontinued the heat lamp about two weeks ago. My target is to have them out in the coop within two weeks. It'll be warmer here and they'll have more of their adolescent feathers.

 

I have found that when I put the heat lamp in the middle they ahve more room and dont pile up. I stopped putting it in corners where piling is more likely. You could try that put it so it hangs in the middle of the coop instead of one corner.

 

Also, could there be any drafts coming in? Can you board up any windows that might be letting cool air in at night?

I'm pretty liberal on the side of letting chicks that age have at it without a heat source, etc., but if you think the one you lost was suffocated from the piling, then the only explanation i know if is that they are cold.

I agree with putting the light in the middle in this case too.