There are ordinary bird-watchers and there are
'twitchers'. Each autumn this strange breed descends on the Isles of Scilly in search of its quarry. Sue Hicks joined last year's migration and discovered that twitchers have their own language and plumage, and are driven by an instinct to 'tick' as many species as possible, for the longer the tick-list the more important you are.
Producer ANDREW VIVIAN BBC Bristol (R)