Blackburnian warbler in Cornwall:
https://www.walesonline.co.uk/news/uk-news/uk-twitchers-floc...
https://www.walesonline.co.uk/news/uk-news/uk-twitchers-floc...
Especially the flock of bird watchers...
https://i2-prod.birminghammail.co.uk/incoming/article2527920...