Sometimes when I fill my bird feeders in late afternoon, I notice the food is gone by morning. When food vanishes overnight, I suspect deer, raccoons, opossums and flying squirrels are the likely culprits. But when seed disappears during the day, feathered seed-hoarders may be responsible.
Years ago I learned about seed-hoarding birds by watching a white-breasted nuthatch as it repeatedly harvested acorns from a white oak tree. Often it took a single acorn, flew to a nearby perch, wedged the nut in a crevice in the bark, then hammered the acorn with its dagger-like bill and extracted the meat.
Just as often, however, the nuthatch didn't eat the acorn. Instead it flew to a nearby snag and stashed the nut behind a slab of peeling bark. The first time I observed this I peeled off of a piece of bark and a handful of acorns poured onto the ground. The nuthatch was storing about half the acorns it collected.
Chickadees, titmice and woodpeckers also sometimes store food in roosting cavities when weather gets cold and snowy. I've occasionally found such caches during midwinter nest box inspections.
Once I watched a red-bellied woodpecker make repeated trips to a knothole on an abandoned outhouse. Each time it dropped a mouthful of sunflower seeds through the knothole.
It inserted its bill into the hole, and then returned to the feeder. After jamming its mouth full of seeds, it returned to the outhouse and dropped the seeds through the knothole. After watching this for several minutes, I opened the outhouse door and found a pile of sunflower seeds on the floor. What the woodpecker failed to understand was that the seeds were not retrievable unless it could later get into the outhouse.
This reminded me of classic food caching behavior by acorn woodpeckers, which are native to the Southwest. They collect and store acorns, and in one published account, an industrious acorn woodpecker made its daily deposits in a knothole on the wall of an abandoned cabin. But those acorns didn't go to waste; the cabin's mice surely enjoyed the easy meals.