Looking at this again, I think it could possibly be a Short-toed Treecreeper. I didn't hear it call, but is anyone able to tell just looking at the picture?
from some random googling it seems like you would need the call to tell them apart properly. However, I did find this:
"Where the two species overlap, the Common Treecreeper is generally found at higher altitudes and in coniferous woodland. In fact the Germans call the Short-toed Treecreeper the ‘Garden Treecreeper’."
There *are* minor visual differences, but it's tricky to notice them unless you either see the bird at very close range, or see individuals of both species side by side.
That said, I think this individual does look "right" for a Short-toed, though I cannot be 100% for obvious reasons.
Today I went back to the same place as I saw the treecreeper pictured above and I managed to spot a treecreeper in the same patch of woods, which I was able to confirm was a Short-toed with the call.
So it seems likely that the one in the picture that I saw last year was also a Short-toed.
You can distinguish them based on the wing pattern (see your Collins field guide for details ) and the wing pattern for this one looks perfect for short-toed treeceeper.
You can distinguish them based on the wing pattern (see your Collins field guide for details ) and the wing pattern for this one looks perfect for short-toed treeceeper.
Saw my first ever Short-toed Treecreeper last year in the grounds of Tiergarten Nürnberg fortunately I saw it at extreme close range, so I was able to identify it visually.