Definition of "mutation"

Plant breeding is always a numbers game. […] The wild species we use are rich in genetic variation, […]. In addition, we are looking for rare alleles, so the more plants we try, the better. These rarities may be new mutations, or they can be existing ones that are neutral—or are even selected against—in a wild population. A good example is mutations that disrupt seed dispersal, leaving the seeds on the heads long after they are ripe.

2013 May-June, David Van Tassel, Lee DeHaan, “Wild Plants to the Rescue”, in American Scientist‎, volume 101, number 3, archived from the original on 14 August 2013

Birdwatchers would enjoy a host of sparrows, a herd of swans, a descent of woodpeckers, a herd of wrens, and mutation of thrushes.

1984, Virginia Wildlife, volume 45, Virginia Commission of Game and Inland Fisheries

Names for a group: A flute or mutation of thrushes.

2010, Doug Bennet, Tim Tiner, The Complete Up North: A Guide to Ontario's Wilderness from Black Flies to the Northern Lights, page 57

A Mutation of ThrushesThe authors of the books of venery were not predicting Darwin with this term, but taking a cue from a common fable of the time.

2013, Jason Sacher, A Compendium of Collective Nouns: From an Armory of Aardvarks to a Zeal of Zebras, page 196