Hi,
I was born in, and grew up north of, Düsseldorf. Birding in that area is suboptimal, given the very dense population and the large number of cities in very close proximity. In fact, the lack of adequate bird protection areas in the province of North-Rhine-Westphalia (of which Düsseldorf is the capital) has been the cause of enforcement proceedings by the EU Commission against Germany at the European Court of Justice for violation of the bird protection directive. But you don't have to go too far for some decent birding if you're not looking for terribly rare species. My favorite spot is in the town of Mülheim an der Ruhr, just about twenty minutes to the northeast of Düsseldorf. Just south of the Mülheim city center, along the west bank of the Ruhr river is a nature preserve for birds (Ruhraue Mülheim). You can usually always find several Grey Herons, Great Crested Grebes and various waterfowl in the area. In the summer there are also numerous warblers and Long-tailed Tits. Not sure what you'll find in January/February, though.
As to historical wonders, there isn't that much in Düsseldorf proper (the town is more suited for shopping for clothes on the Kö and drinking beer in the Altstadt). But if industrial history interests you, you should check out the
Route der Industriekultur. This route will take you around the old steel factories and coal mines of the Ruhr valley that fueled German industrialization. Most of these are now defunct and many of them now lead a second life as performance spaces, galleries or landscape parks. The route also includes Villa Hügel, the immense former mansion of the Krupp family. An excursion to some of these sites (the Villa Hügel, Landschaftspark Duisburg Nord and the Zeche Zollverein are really worthwhile) can be easily combined with a birding trip to the Ruhraue in Mülheim as these are all fairly close to each other.
If you do decide to trek out a bit further afield, I would highly, highly recommend the
nature preserve Hoge Veluwe in Holland near the town of Arnhem. It's only about an hour, hour and a half drive from Düsseldorf. The nature is magnificent, you can rent free white bikes to get around the preserve and there is a fantastic little art museum in the middle of it (the Kröller-Müller Museum) that has one of the finest Van Gogh collections in the world, including most of his surviving sketches, which are, however, not always on exhibit due to their sensitivity to light.
BTW, Dieter, to English-speakers Karl der Grosse is known for some reason by his French name, Charlemagne.