> you can see some very early social behaviors.

Here's a more cynical take on this:

As a chick, I'd do the same, hatching just after the first. So the first-hatched would keep any predator busy while I get out of my shell and improve my own chances of survival.

It compares to zebras running close-packed, each improving its individual chances because the lion will catch only one.

Edit: Thinking further, I concede that there could be a big overlap between social behavior and selfish gene survival. For example, the first to hatch could be helping out its siblings by offering itself up to a predator.