What causes black chicken poo?

Like a number of the posts on this site, this entry is intended to help others seek the information that took me an awful lot of googling to get to. The chickens have been doing black oily droppings that are somewhat pungent in smell. The question of what causes black chicken poo has been posed several times on the web but there are no definitive answers. Usually it appears to be caused by consumption of darkly coloured berries but a hunt around the ground and bushes did not reveal any culprits. The two remaning causes are not good. Firstly that it's a sign of severe malnutrition (seems unlikely). Secondly that it's blood passing through the digestive tract signifying an upper gastrointestinal bleed (melena or melaena). In view of the smell I fear the latter. Neither sound good and the literature suggests they will die within a couple of weeks.

Two weeks on and they are healthy as anything and I've discovered the cause of the black droppings. The chickens appear to have been eating the elderberries from a tree in the corner of the garden. There had obviously been elderberries falling to the ground which they'd been devouring. Once all the elderberries had gone, the nasty runny black poo went too. There's a saying in medicine that 'common things happen commonly'. It often helps, when faced with a confusing situation, to recheck the basics!