What caused 6 chicks to die, in a pile, at the same time?

[Ebz5003]

I have 36 4 week old chicks living in a 6 chicken coop that is attached via hardware cloth to an outdoor brooder/ cage that is completely covered with .5 inch hardware cloth and all doors locked at night. I opened one of the nesting box doors this morning to find around 10-15 live chicks crowded into one of the nesting boxes and underneath these was a pile of six dead chicks. They were still warm and completely intact. Two had broken necks, but there was no blood or signs of predators whatsoever. It was unusual to see them crowded inside that coop instead of scattered foraging inside and outside. Could it be that they saw a predator outside and then crowded inside into the nesting box, suffocating the 6 chicks in the process? Is this overcrowding? I have since removed ten more chicks and put them safe in the garage and also removed nesting box dividers, to make more room. We are moving soon, and they'll have more space.

 

[nuthatched]

That's sad, I'm sorry.
How do you know they had broken necks? Its likely they were smothered by the others.

 

[Ebz5003]

That's sad, I'm sorry.
How do you know they had broken necks? Its likely they were smothered by the others.

Two had necks that literally flopped over to the side when you pick them up. The others were simply limp. Yes, I'm sorry I wasn't there to save them.

 

[nuthatched]

Two had necks that literally flopped over to the side when you pick them up. The others were simply limp. Yes, I'm sorry I wasn't there to save them.

That's normal for dead chickens. They were the warmest so rigor hadn't set in as much yet