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
Swan goose in collections, and escapes are not unusual amongst feral flocks of other "Anser" and "Branta" geese. The swan goose is large and long-necked for its genus, wild birds being long (the longest "Anser" goose) and weighing or more (the second-heaviest "Anser", after the greylag goose, "A. anser"). The sexes are similar, although the male is larger, with a proportionally longer bill and neck; in fact the largest females are barely as large as the smallest males. Typical measurements of the wing are in males, in females; the bill is about long in males and in females. The tarsus of males