Black-Striped Sunflower Seeds
There are two types of sunflower seeds commonly found in birdseed -- oil-type or oilseed and black-striped or confectionery sunflower. Mourning doves generally refuse the black-striped variety according to the Virginia Cooperative Extension. Oil-type sunflower seeds have all black husks. The shells are easier for a dove to crack and the seed has a much higher fat content than black-striped sunflowers.
Most birds do not eat flax seeds, let alone mourning doves, according to Cornell Lab of Ornithology. Flax seeds are tiny, flat, oval or tear-drop shaped seeds that are pale gold or tan in color. Only a few kinds of finches are known to eat flax seed.
Canary seed is eaten by some wild birds such as the brown-headed cowbird and the house sparrow but it is usually ignored by mourning doves. Canary seed is flat, almond-shaped and tiny. It's so tiny that it's too small for the doves to see it. Canary seed is native to the Mediterranean, which may be why mourning doves tend to ignore it. The North American dove just has not evolved to the point to search for or scratch the ground for an unfamiliar seed.