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
Anser (bird) Maltese swan "Cygnus equitum" was occasionally placed into "Anser", and "Anser condoni" is a synonym of "Cygnus paloregonus". A goose fossil from the Early-Middle Pleistocene of El Salvador is highly similar to "Anser". Given its age it is likely to belong to an extant genus, and biogeography indicates "Branta" as other likely candidate. ?"Anser scaldii" (Late Miocene of Antwerp, Belgium) may be a shelduck. Two species in the genus are of major commercial importance, having been domesticated as poultry: European domesticated geese are derived from the greylag goose, and Chinese and some African domesticated geese are derived from the swan