I have now downloaded and installed both apps, but have not yet had the time or leisure to take a closer look or even try them out.
Both are also available in German language. The Cornwell University is indicated, but also German developers. I assume that they have filled the apps with local (bird) data.
I am curious and will report!

Yes, in winter I also hear birds. Especially when they warn their fellow birds because a hungry buzzard or hawk is nearby.... The cheerful chirping, which we know from spring (then because of the courtship particularly strong) and summer, falls rather away. Costs the feathered friends too much energy, when they should rather shiver themselves warmly... ;-)