My chickens, 2 red sex-links and one white leghorn, seem to be eating the straw out of their nesting box! I put in new filler, and they either knock it to the floor, or it disappears. Then all we can hear are their claws scratching at the nesting box. Is there something else I should put in instead??? This is a new behavior, they've been laying on the straw no problem for months now.... Any insight would be appreciated! Thanks!