The bird is either a Short-toed Treecreeper (Certhia brachydactyla) or a Eurasian Treecreeper (Certhia familiaris) - info I found them described them as nearly indistiguishable by look, and I did not hear it make any sound.
I'm afraid the tree bark is better in focus than the bird, but I liked the patch of light the bird was sitting in, so here it is anyway.
Postwork: Cropping down to ca. 75% of original image.
Comments and feedback are always appreciated!