The Eurasian nuthatch or wood nuthatch (Sitta europaea)
Nuthatch is always looking for food, they are always busy looking for it. Even when they are full. That's only when they do not want to eat, they are looking for food in order to stockpile for cold hungry times.
Sometimes they find supplies of other birds, such as Coal Tit, Willow Tit, or Jays, and then they hide them in other places.
What I could capture in the photo. He found someone's cache with a seed. He pulled it out and hid it in another place.