Two Trees

Sunny all day and no snow and I went walking in the Elendsklamm. No Klamm photos today, but two trees.
When I spotted something red on the tree in the main photo, I couldn't make out what it was - until I zoomed in. An insect hotel in the woods me thinks, but why? For a special insect? Any other ideas?

The extra shows one of the trees with the scallop shell, the symbol of the Camino (the Pilgrims Way of St. James) to Santiago de Compostela in Spain. Walked for a little while on the Palatinate route of the Camino whichs runs through the Elendsklamm.

20:15; 7°C