The oil based substance? was a fine layer stuck to the inside of the 5 gallon drum. Which MISTAKENLY got filled with water, as we all Know oil is lighter than water, So once poured into drinkers oil will float to top so when birds take a drink there probally drinking very little if any oil? But wattles and head will get some on them. The water to oil Ratio is in far greater favour of the water. The worse possibility is for any bird that took a drink during the mixture getting poured or before settlement. MY TAKE ON IT Has anybody ever used garlic oil, medicated creosote or similar, wattles go dirty on night of administration next day clear and pink.