Foxes sneak into your sims' coops and steal eggs at night or early in the morning. I've even seen them carrying the eggs in the mouth (usually they drop the eggs if challenged or shooed, in my experience). If they enter it, the coop will rock back and forth with feathers flying in their air and the chickens squawking in agitation. Foxes have also been known to attack chickens if there are no eggs to steal.
The two times this happened to me, the rooster and the hen were both able to fight them off successfully, luckily; they were "young adult" fowl (who were also very happy, full and contented at the time) so that may have been the reason why.
The cloud you're seeing could be a fight with a chicken. I have also found my camera will automatically go over to an elder fox who is dying, which is also annoying.
