“I asked Bernd Heinrich if he knew why feeder birds, like finches, discard so many seeds. It turns out he and other scientiests did research on this back in the 1990s – of course, he did -measuring discarded seeds with painstaking accuracy. The short answer: Songbirds prefer shorter, fatter unshelled sunflower seeds, more depth than length, because they contain more oil. They take half a second to judge the seeds, dropping the low-density ones, until they find a seed to their liking.”
