Long-tailed skua - Stercorarius longicaudus
There have only ever been three records of this species in Berkshire:
Wraysbury Res, 30 August 1978 - an immature passing over the extreme east of the county (although the report states that some doubt must remain as to whether it did cross county air space)
QMR, 17 August 2003 - a dark phase juvenile, departing early in the afternoon
QMR, 9-17 September 2006 - a dark phase juvenile, found late afternoon
All three birds were found by the phenomenal Chris Heard!