Vagrant
A bird which wanders to a particular area if its orientation is at fault or adverse winds drive it off course but in normal circumstances would not be found there at all. Vagrants are also called 'accidentals' or 'casuals', and in the British Isles are usually defined as species which have been recorded less than 20 times. These islands are well placed to receive vagrants from various directions and a large proportion of the British List is made up of them.From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver