Twice a year, in spring (mid-March to mid-April) and autumn (mid-September to mid-October), enormous flocks of starlings — often a million birds or more — gather over the salt marshes south and west of Ribe to roost in the reedbeds. At dusk they perform spectacular coordinated murmurations against the setting sun, hence the name Sort Sol, "Black Sun."
The phenomenon is unpredictable but well-monitored: the Wadden Sea Centre runs nightly tours during the season, and the bird hides at Aventoft and Mandø causeway are reliable viewing spots. Bring warm and waterproof clothes; the marsh wind can be brutal even in April.