OSM Boundary Map Node - Nature Protection Area/Boundaries

I have list of bird observations with geographic coordinates (longitude/latitude) in the town Ulm in Germany. I want to filter this list to include those collected within an nature protection area using the geographic coordinates. I thought I could use "Geo-Coordinate Row Filter for this purpose. But how can I retrieve the boundaries of the nature protection area as a polygon to filter the data? I failed to retrieve the boundaries using “OSM Boundary Map” node. Is there a way to retrieve that data using this node or any other node? (I am able to see the nature protection area „Lichternsee“ in Open Street Map). Many thanks in advance, Andreas