The Eurasian nuthatch or wood nuthatch (Sitta europaea)
He found someone's hidden seed in an old log and decided to hide it.
Maybe even he himself hid it here earlier and found it again.
I don鈥檛 know whether they have a good memory or not, whether they remember all their caches, but judging by their behavior, they simply forget most of their caches. This behavior, I mean "stocking", helps birds a lot in cold weather, especially in winter. They roam the forests and find caches with seeds.