She's Feeling Broody

I've been keeping my chickens inside their coop and run lately.  With a hungry red fox in the neighborhood who has already eaten one chicken, it's safer for them to be confined.  I feel bad for them because they can't get much exercise and can't take many dust baths.  When I check on them in the afternoon I bring them some fresh cold water and a handful of dandelion leaves to munch on.  When I collect the eggs one chicken is always sitting on them.  Since the Buff Orpingtons all look alike to me, I can't tell for sure if it's the same chicken sitting on the eggs.  I suspect it is the same chicken because she makes the same purring noise when I open the egg collecting door.  She also behaves the same when I open the door.  She sits facing south.  When the door opens she puffs out her feathers and makes herself look 25% larger than she is.  She doesn't cooperate when I push her aside to collect the eggs.  She plants herself firmly on the eggs.  Once I have the eggs out she will stand up and leave the coop to get some fresh air and a drink of water.  I think she must have a strong broody disposition to stay in the coop during this weather.  I have to admire her.  She's trying to be a good mother.