Duane Doty State College, Pennsylvania Striped sunflower seed is larger than black oil sunflower, but black oil seeds have thinner shells and a higher percentage of fat content per weight.
Studies show that birds prefer the black oil to the striped varieties.
You also can buy sunflower seed with the hulls removed, known as chips or hearts. Many birds seem to like this best of all. It also eliminates the accumulation of hulls beneath the feeders. As I watched a blue jay dominating my sunflower feeder, he appeared to be gulping so many seeds at one time that his throat actually bulged. They have been observed taking more than 50 seeds at one time before flying off.