Andrew Parkinson / Arctic Tern (Sterna paradisaea) in flight chasing Arctic Skua (Stercorarius parasiticus) that has stolen its food. Scotland, UK, July. (non-ex)

Andrew Parkinson / Arctic Skua (Stercorarius parasiticus) pair stealing fish from Arctic Tern (Sterna paradisaea) Shetland Islands, Scotland, UK, July. (non-ex)

Andrew Parkinson / Arctic Skua (Stercorarius parasiticus) pair stealing fish from Arctic Tern (Sterna paradisaea) in flight, Shetland Islands, Scotland, UK, July. (non-ex)

Andrew Parkinson / Arctic Skua (Stercorarius parasiticus) pair almost colliding in flight, as they pursue an Arctic Tern (Sterna paradisaea). Shetland Islands, Scotland, UK, July. (non-ex)

Edwin Giesbers / Arctic tern (Sterna paradisaea) in flight, vocalising, aggresive behaviour, Farne Islands, Northumberland, UK, June

Edwin Giesbers / Arctic tern (Sterna paradisaea) Farne Islands, Northumberland, UK, June

Edwin Giesbers / Arctic tern (Sterna paradisaea) in flight, calling, Farne Islands, Northumberland, UK, June

Edwin Giesbers / Arctic tern (Sterna paradisaea) in flight, Farne Islands, Northumberland, UK, June

Nick Garbutt / Arctic tern (Sterna Paradisaea) hovering in flight over an iceberg.Peterman Island, Antarctic Peninsula, Antarctica. February.

David Woodfall / Flock of Arctic terns (Sterna paradisaea) in flight, Long Nanny reserve, Northumberland, UK

Guy Edwardes / Arctic Tern (Sterna paradisaea) in flight over nesting colony, Isle of May, Firth of Forth, Fife, Scotland

David Woodfall / Arctic terns (Sterna paradisaea) in flight with a researcher walking, in mist, Northumberland, UK, June 2009