aberrant

Differing from the norm.

Straying from the right way; deviating from morality or truth.

Deviating from the ordinary or natural type; exceptional; abnormal.

The more aberrant any form is, the greater must have been the number of connecting forms which, on my theory, have been exterminated.

A person or object that deviates from the rest of a group.

A group, individual, or structure that deviates from the usual or natural type, especially with an atypical chromosome number.

Also I think other birders realise you are struggling a bit when you start talking about aberrants[.]