Barnacle goose were of the same nature as other birds. The question of the nature of barnacle geese also came up as a matter of Jewish dietary law in the Halakha, and Rabbeinu Tam (1100–71) determined that they were kosher (even if born of trees) and should be slaughtered following the normal prescriptions for birds. The mythical barnacle tree, believed in the Middle Ages to have barnacles that opened to reveal geese, may have a similar origin to the other legends already mentioned. Barnacle goose The barnacle goose ("Branta leucopsis") belongs to the genus "Branta" of black geese, which contains species with
Branta correctly assigned – meaning that the genus "Anser" was once much more widespread than today and that it coexisted with "Branta" in freshwater habitat which it today does only most rarely – is not clear. Especially in the case of "B. dickeyi" and "B. howardae", doubts have been expressed about its correct generic assignment. The former ""Branta" minuscula" is now placed with the prehistoric American shelducks, "Anabernicula". On the other hand, a goose fossil from the Early-Middle Pleistocene of El Salvador is highly similar to "Anser" and given its age and biogeography it is likely to belong to that genus