My hen puts straw on her back after laying an egg. Why?

[Red]

Some of my girls do that - even our ex-battery girl did that when she laid an egg in the run (never figured out how to use a nest box)...i figured it was something to do with camouflaging / hiding, but no idea what??

 

[shelleyb1969]

My little bantam orp pullet was sitting in her "nest" today, getting ready to lay her first egg. She's been preparing herself for a few days now. She got up off of her nest and began picking feathers off the floor and putting them on her back. Since she's never layed an egg herself, nor has she ever seen another hen lay one, I'm confused as to why she's doing this. Maybe she is trying to hide herself so I can't watch her?