Significance
Black oil sunflower seeds have much thinner shells than striped sunflower seeds. This makes them much easier to open, so pigeons and other seed-eating birds prefer them over striped sunflower seeds. Pigeons may eat striped sunflower seeds if they are hungry enough. Domesticated pigeons and racing pigeons will also eat black oil sunflower seeds, according to "Pigeons."
Problems
Sunflower seeds attract a wide variety of seed-eating birds, but pigeons may scare off smaller birds like chickadees, sparrows and cardinals. If pigeons are becoming pests in a yard, there are several things you can do to deter them and still feed the bird species you want to attract. Pigeons prefer to eat off of the ground, so never use table feeders. Hang up globe-shaped feeders and remove the perches, advises the Massachusetts Audubon Society.
Diarrhea
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. If wild pigeon droppings become a problem in a yard, switch to globe feeders to discourage them from eating and defecating on your property. Switch to other types of seeds, if possible.
Shelled Vs. Hulled
Some people prefer to place hulled sunflower shells in their feeders because there aren't piles of empty shells to clean up afterwards. It is necessary to remove these shells daily in order to prevent them from attracting vermin like rats. Sunflower seeds with their shells still on are healthier to feed wild birds than hulled or shelled seeds. If buying a mix, check to see that it does not contain hulled sunflower shells or sunflower seed pieces. When out of their shells, sunflower seeds spoil rapidly. They also are more prone to getting wet and growing bacteria that could kill wild birds, including pigeons.