These birds are in my greenhouse looking for insects they are in no danger from chemicals because there are none, I don’t use any chemicals just fresh water  I realise that if you have a balanced environment then chemicals are not needed I accept if you have a higher density of fish some chemicals are required to maintain health however they must be kept to a minimum we are farming water just as much as fish good water equals good fish. It follows that if we wish to have these balanced and diverse ecosystem in the wild we must keep chemicals out of our environment and of course our water.Blackfish have a habit of stirring up the detritus on the bottom of there habitat and then trawling back through it to collect any food that may have been dislodged this behaviour could be a reason why they are exposed to higher levels of toxins than other species of fish.  I think these birds are a type of finch.