Vejlen was previously a fjord connected to the sea, but in 1765 a dyke and sluice were built, cutting off the fjord. Vejlen was drained to create pastureland. In 1905, the sea broke through the dyke. Even though the dyke was reconstructed, Vejlen never became completely drained again. A very shallow lake was formed, that is now brackish and very rich in nutrients, due to pollution from the surrounding farmland. Different waterbirds breed in Vejlen, including Little Grebe, Red-necked Grebe, Avocet and Common Redshank. Marsh Harrier breed here just about every year. Bearded Tit nest here, and Common Kingfisher can be seen throughout the year. In summer Reed Warbler, Icterine Warbler, Greater Whitethroat and Reed Bunting can be heard singing in the scrub. During migration the lake and the shallow waters off the coast hold many species of wader. European Golden-Plover can be seen both spring and autumn in flocks of up to several thousand birds standing on the fields in the vicinity. Other waders include Northern Lapwing and Eurasian Curlew in quite large numbers, and smaller numbers of Eurasian Oystercatcher, Dunlin, Ruff, Snipe, Spotted Redshank and Common Greenshank. In winter several hundred Whooper Swan and a few Tundra Swan (Bewick's Swan) turn up.
From Svendborg, drive south on route 9 in the direction of Rudkøbing. In Bregninge, turn off to the the right and follow the signs to Nørre Vornæs. In Sønder Vornæs, turn onto Sønder Vornæsvej and after a few hundred metres onto the Vejlenvej, where there is a lay-by. From here, a path leads to a bird hide.