Occasionally a nuthatch will sit in or on a feeder, probing deeply into the slots that release the seed after some particular delicacy. The bird throws out seed right and left, which I’m sure the squirrels and juncos on the ground below appreciate.
I’m not sure what the bird is after, but when one seed strikes its fancy, and the bird flies off to the nearest tree. Sometimes there seems to be nothing in its bill as it leaves the feeder, but I saw the bird pick up a seed, so it must be holding it in its mouth.
Sure enough, the nuthatch jams a seed into the crack of the tree. I initially thought it was caching the seed there (wrong conclusion!), but obviously failed to watch the whole operation carefully. No, the nuthatch jams the seed into a crack to hold it there securely while the bird proceeds to drill it, and quickly extract the nutmeat inside.
Aha! This is how you eat seeds when “perched” upside down on a vertical surface without having to use your feet to hold the seed like a chickadee would or use your large, nut-cracking bill and tongue the way a cardinal would.
A reminder to me to conduct more thorough observations before making a hasty conclusion.