Barnacle Goose: The Bird That Was Believed to Grow on Trees

Mar 18, 2020 0 comments

Barnacle Goose

In the days before it was realized that birds migrate, ancient scholars struggled to explain why some species of birds appeared and disappeared as the seasons changed. The idea that these little feathered creatures can travel thousands of miles in search of food and warmth was unimaginable. But the notion was not entirely an alien one.

Greek writer Homer believed that cranes flew south in winter to fight the pygmies of Africa, a fable that’s repeated by Roman naturalist Pliny the Elder. According to Pliny, these pygmies fought the cranes with arrows while mounted on goats and rams. Aristotle suggested that the tiny swallow avoided the strain of migration by hibernating in the ground instead. These myths were kept alive for centuries. In the 16th century History and Nature of the Northern Peoples by Swedish Archbishop Olaus Magnus, there is a passage on swallows that say that the bird congregate in vast numbers in fall, and sink down into the mud and water, packed like sardines. A woodblock print accompanying the passage shows fishermen pulling up a net loaded with hibernating swallows from a lake.

Aristotle even went so far as to suggest that some birds underwent miraculous transmutation as the seasons changed. He declared that the European Redstart, which is commonly seen during summer, transforms into the European Robin when the weather turns cold. In reality, the Redstart flies south to Africa for the winter, while the Robin, which breeds farther north, comes to Greece in winter.

Another bizarre animal fable that was born through a comedy of errors was that of the barnacle goose.

Barnacle Goose

A Barnacle Goose. Photo: Grisha Bruev/

In his Topographia Hibernica, published in the late 12th century, Gerald of Wales attempted to explain why nobody had ever seen the barnacle goose (Branta leucopsis) breed:

There are likewise here many birds called barnacles, which nature produces in a wonderful manner, out of her ordinary course. They resemble the marsh-geese, but are smaller. Being at first, gummy excrescences from pine-beams floating on the waters, and then enclosed in shells to secure their free growth, they hang by their beaks, like seaweeds attached to the timber. Being in progress of time well covered with feathers, they either fall into the water or take their flight in the free air, their nourishment and growth being supplied, while they are bred in this very unaccountable and curious manner, from the juices of the wood in the sea-water. 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. No eggs are laid by these birds after copulation, as is the case with birds in general; the hen never sits on eggs to hatch them; in no corner of the world are they seen either to pair or to build nests.

What Gerald saw were actually goose barnacles, a crustacean that live in the sea attached to rock surfaces and timber and often wash up on shores along with pieces of driftwood. The bulbous white shells and black stalks of these sea-creatures were mistaken by medieval people for the neck of a still-transmuting goose. The barnacle goose mainly winters on the Atlantic coasts of Scotland and Ireland, but in summer it travels north to the Arctic and breeds on its many islands. The fact that the goose was never seen to breed gave rise to the myth that it spontaneously generated from barnacles.

Barnacle Goose

Drawing from the manuscript of Topographia Hibernica by Gerald of Wales.

The legend was furthered by Pope Pius II, who travelled to Scotland in the 15th century and wrote:

I heard that in Scotland there was once a tree growing on the bank of a river which produced fruits shaped like ducks. When these were nearly ripe, they dropped down of their own accord, some onto the earth, and some into the water. Those that landed on the earth rotted away, but those that sank into the water instantly came to life, swam out from below the water, and immediately flew into the air, equipped with feathers and wings.

The extravagant legend of the barnacle goose was eagerly embraced by some Irish clerics, because it gave them a convenient excuse to introduce meat to their plates during periods of fasting without offending Christian morals. Because the fowl was not born of flesh, they argued, it was acceptable to eat the barnacle goose at times of fasting. Others expressed doubt. Pope Innocent III explicitly prohibited the eating of these geese during Lent, arguing that despite their unusual reproduction, they lived and fed like ducks and so were of the same nature as other birds.

goose barnacles

A goose barnacle. Photo: Hans Hillewaert/Wikimedia Commons

goose barnacles

Goose barnacles on wood. Photo: Patiparn46/

The Holy Roman Emperor Frederick II was skeptical of the legend. He examined the barnacles and noted no evidence of any bird-like embryo in them. His remarkable observations and comments are worth quoting:

There is also a small species known as the barnacle goose, arrayed in motley plumage ..., of whose nesting haunts we have no certain knowledge. There is, however, a curious popular tradition that they spring from dead trees. It is said that in the far north old ships are to be found in whose rotting hulls a worm is born that develops into the barnacle goose. This goose hangs from the dead wood by its beak until it is old and strong enough to fly. We have made prolonged research into the origin and truth of this legend and even sent special envoys to the North with orders to bring back specimens of those mythical timbers for our inspection. When we examined them we did observe shell-like formations clinging to the rotten wood, but these bore no resemblance to any avian body. We therefore doubt the truth of this legend in the absence of corroborating evidence. In our opinion this superstition arose from the fact that barnacle geese breed in such remote latitudes that men, in ignorance of their real nesting place, invented this explanation.

Frederick II’s contemporary Albertus Magnus went even farther and actually bred one with a domestic goose. Albertus dismissed the legend as “altogether absurd”, noting that he and his friends had “seen them pair and lay eggs and hatch chicks.” That was in the 13th century. Yet, the absurdity survived for five more centuries with many naturalists giving credit to the story. It wasn’t until Dutch sailors had travelled to northern Europe and saw the birds breed, that the legend was finally led to rest.

# The Engines of Our Ingenuity,
# Topographia Hibernica,
# Shorelines,
# John S. Wilkins, Species: A History of the Idea
# The Barnacle Goose Myth in the Hebrew Literature of the Middle Ages,


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