With their quadruple personalities, those little brown birds at your feeder are a lot more interesting than they might appear.
I am not a bird person but this is legit fascinating. They buried the juicy bit down at the bottom of the article.
Field researchers noticed over 25 years of research that the two color morphs of this species *nearly always* cross-breed with each other, so they dug into the genetics and discovered a supergene that influences hormones that influences behavior to the point where there are effectively FOUR sexes of these birds!
(Actually good) explainer video from the original paper:
(Go go basic science research! Sometimes you need to look at things close enough to realize there’s something interesting going on — originally they thought the morphs were juveniles!)