From the platform at Ballum Sluse you can watch all kind of waders, ducks and geese in the low waters between the Wadden Sea island of Rømø and the mainland. As well as White-tailed Eagle always in numbers. (The locals I talked to while I visited the site claimed to have had 80 White-tailed Eagle in one day.) Common Starling can be seen in huge numbers, followed by the various falcons chasing them. Any size flock of migrating birds will pass in spring and fall. It is is one the few areas in Denmark with breeding Montagu's Harrier.
The site has excellent overview, but on a sunny day arrive early - as at noon time, the sun will start to blaze into your face.
You can park right at the spot.