Ever watch the birds at your feeders sort through the seeds, tossing several to the ground before choosing one to eat? Tests have shown that when selecting seeds birds will examine several and take the heaviest. Blue Jays have been tested by loading peanut shells with b-bs, weight varying. Always,The birds seem to find the investment in energy to secure food pays a bigger dividend when a larger item is selected. And the difference one sunflower seed to another has to be very subtle.