Black Tern Chlidonias niger
Scarce/fairly common passage migrant in spring and autumn. American Black Tern C.n. surinamensis is a vagrant (BBRC).
A familiar passage migrant recorded more frequently in autumn than in spring and in very variable numbers. It is regularly seen on inland waters as well as on the coast. The Atlas notes that large numbers used to nest in the Fens before drainage and they last bred in Crowland Wash in the 1840s. In more recent times a pair built a nest at Bardney Ponds in 1961. Early migrants appear from late April but the main passage lasts from early May to early June and in autumn August-September and while most larger flocks are of the order of 20-40 some as large as 100 or more have been recorded. Most have moved through by the end of September with stragglers into October or, exceptionally, November.
An American Black Tern, C.n. surinamensis was present at Covenham Reservoir September-October 2011. This record is covered in a separate account.
(Account as per new Birds of Lincolnshire (2021), included September 2022)