"Birds of a feather flock together"

There is ample testimony here at Solitaire that birds of a feather flock together. These tiny birds come in groups.  They are many in number.  Here we see four of them. The three have not gone in but are waiting for the fourth one who has just arrived.

This is no different from teenagers having the same mentality.  They will never do anything alone.  Friends get together to enjoy any activity. 

Summer has just about started and birds have already lined up for a cool dip.