I am working on a multifactorial model to explain preferences for a given habitat for a species of bird, on a European scale. In this model, I have included variables such as slope or terrain ruggedness, which caraterize mountain habitat. However, I would like to be a little more precise regarding presence of rocks, boulders, screes, or anything related to broken rock fragments. My research has been unsuccessful so far, I could only find lithological maps, which is not quite my goal.
Do you know if such maps exist? Or is there a proxy that I have not thought about?
I am new to habitat modelling, so any help would be greatly appreciated!
(I use both QGIS and R)