Your budget probably won't get you a bucket full of lenses. For the digital cameras, the Pentax 12-24mm is a great wide angle. Telephotos can be had used, some autofocus and some not. For birds, lood for 200mm or greater, and if you can manually focus, there are 200mm A lenses that are very good.
There is a 300mm f/4 but the price has gone through the roof now that the K10D is out, too bad. They were some of the finest lenses you could get used!