The ferals that come to my yard eat the black oil sunflower seeds with no seemingly ill effects, but even though I do give mine a small amount of the black oil, I only use the hulled for my birds. Shouldn't use many as they are high in fat, but they do cantain other good things as well. In the amount that you should be adding to their feed, it isn't all that expensive to buy the hulled.
Right after I was diagnosed with Pigeon Breeders Disease I fed Straight Black Oil Sunflower seeds for an extended time period. The birds love them and do great on them. I actually believe that the fiber from the hulls is good for them from a nutritional and digestive point.
I have and will always use it as a good percent of my feed mix.
I did not like the dark stool it left, and because pigeons don't shell their seeds, I leave it out.. hulled chips are fine.. I wonder why they do not add inshell sunflower seeds in pigeon grain mixes?. as treats..Im sure they are fine..here is one quote.
" Black oil sunflower seeds are used for making sunflower oil, hence their nickname "oilers." The seeds' oil will give pigeons diarrhea. Domestic pigeons should only eat sunflower seeds as treats and in very small quantities in order to avoid diarrhea."
I feed during racing, very high fat content. What is interesting is how the fiber affects their droppings. They get smaller and black looking, and yes very solid. If birds have loose droppings, it is not from black oil sunflower seeds, as it has opposite affect.