The Chickens are Unusual

Where I come from, chickens act in a particular way.

But my sister has chickens that don't.  I was looking out the kitchen window onto the chicken run when I saw one of the two writhing in slow morbid death-throws.  She was squatted close to the ground but not completely upright - slighty rolled over to her right side.  Her left leg/foot was spasmodically kicking out in a desperate bid for... something.  Life?
In my concern for the poor dying chook I pointed out her pight to my sister only to learn 'that's what she does...from time to time.'

Huh?
Most chicken's have a dust bath.  These chooks have mud spa/wallow/death thing.

More to this, both these chickens frequent the glass doors to the lounge whenever they are let out of the run and into the garden.  They stand, one at each window panel and peer in as though someone might be in there to grant them entrance.  The strange part being there's no one in the lounge when they do it.

Slightly less strange is their need to stand aboslutely still and on one leg.