Biodiversity values need to be appropriately quantified and thence incorporated in future land development decisions. We assessed the economic and conservation-fundraising potential of vagrant Aleutian Terns in New South Wales, Australia. We found that an estimated 375-581 birdwatchers travelled far (580 ï¿½ 522 km [mean ï¿½ SD]) and reacted quickly (22% of visits were within the first week and 47% within the first two weeks) to see Aleutian Terns in an area where they had never been seen. We estimatedï¿½thatï¿½the total expenditure of these birdwatchers ranged from ? $199,000-$363,000 AUD and we further estimated that birdwatchers would have been cumulatively willing to donate upwards of $30,000 AUD to a non-governmental conservation organisation in order to have viewed the terns. These results suggest that birdwatchers highly value vagrant birdwatching and conservation campaign potential should be explored in future long-staying vagrant bird occurrences.