Barnacle Geese

I adore Medieval flora and fauna mistakes! When they got things wrong, they were so extra about it. So here’s an example of a made-up species that Medieval people thought existed, called the “Barnacle Goose,” or “Branta leucopsis”.

Much like the “Lamb of Tartary,” which I did a different post about, the Barnacle Geese were thought to be an amalgamation of plant and animal — quite literally, geese-like birds that grew upon plants out of pod-thingies that looked like barnacles.

The Ancient Romans and even earlier peoples also thought the Barnacle Geese existed, but sources from pre-Medieval eras are difficult to come by. It was in the Middle Ages that people like Gerald of Wales (late 12th-century) popularized the belief in such creatures.

Writes Gerald: “I have often seen with my own eyes more than a thousand minute embryos of birds of this species on the seashore, hanging from one piece of timber, covered with shells, and, already formed . . . “.

In Medieval Bestiaries (books dedicated specifically to discussing different types of animals), Barnacle Geese made frequent appearances, such as you see here from the late 12th century.

So well known were the creatures that it was rumored (by a man named Beauvais in his 13th-c. _Speculum Naturale_) that the hybrid plant/animal Barnacle Goose caused a conundrum for the papacy, which had to legislate against good Catholics eating the bird during lent (since meat was forbidden but plant-birds were questionable). In fact no such legislation was actually passed.

The most scientific-minded Medieval ruler, King Frederick II of Sicily, wrote about how “there is, however, a curious popular tradition that (Barnacle Geese) spring from dead trees . . . . This goose hangs from dead wood by its beak until it is old enough to fly . . . “, but the ruler doubted their existence.

In fact, what likely happened is that bird migration habits were unknown (those of geese were not understood in Europe until the late 19th century), so it seemed that the geese popped out of nowhere in certain seasons, and the story arose to explain the mystery.