A total of 710,450 observations were made. The study found that black oil sunflower is the most popular seed with most seed-eating birds. Millet is the most popular with sparrows and doves. Since bird populations differ from place to place and change from time to time, it is almost impossible to formulate an entirely satisfactory seed mixture. If you have only one or two feeders, you can probably obtain the best results by offering black oil sunflower seed and white proso millet separately.
Some birds feed almost exclusively four feet or more above ground level on elevated feeders.
Others feed on the ground or on a slightly elevated platform. Still others will feed wherever they can find food. In general, birds attracted to elevated feeders prefer sunflower seed, while ground feeders prefer millet. Tube feeders with small perches should be filled with some type of sunflower seed - black oil, striped or hulled. Usually, birds aren't attracted to tube feeders filled with millet or mixes.