The Prehistoric Sea Swans of Japan


Artist’s impression of the prehistoric sea swan (Artist’s reconstruction from the Gunma Museum of Natural History)

Dear Readers, scientists in Japan have been learning about the lives of two ancient, flightless ancestors of our present-day swans. The first, Annakacygna yoshiiensis, was discovered in 1995, was about the size of the Trumpeter swans of North America (these are the largest existing swans in the world). The second, Annakacygna hajimei,  is smaller, the size of a black swan, and was discovered in 2000.

I know we only had the photo below a few weeks ago, but it’s one of my favourites.

Trumpeter at Wye Marsh in Ontario, March 2019

What is unusual about both these swans is not only that they were flightless, but that their forewings are very short. The scientists involved in the project think that they may have used their wings to cradle their cygnets – modern-day mute swans can be seen carrying their young on their backs in a similar way, and the structure of the wings of the prehistoric species would have made this even easier. Couple this with a mobile tail, and you have a perfect little ‘box’ in which to hold your youngsters in choppy seas.

Photo One by - Own work, CC BY-SA 3.0 at,

Mute swan with wings in ‘piggyback’ position (Photo One)

The swans also had much heavier bones and broader bodies than extant swans – they didn’t fly, so weight wasn’t an issue, while stability in the water probably was.

Skeleton of flightless swan. Note the strange wings! (Photo from Gunma Museum of Natural History)

And finally, these swans were not the delicate grazing birds that modern swans were – they have much heavier beaks which the scientist in charge of the project, Dr Hiroshige Matsouka, compares to that of the shoveler duck. These swans would have fed on sea-going plankton rather than nibbling at grasses, and all in all were very robust birds.

Prehistoric swan at the top, whooper swan at the bottom (Photo from Gunma Museum of Natural History)

These swans must have been amazing birds, perfectly adapted to their marine lifestyle. They date back to the Miocene, 11 million years ago. Who knows what caused their eventual demise? Being flightless is often a liability when things change though – it only takes a new predator, or a problem with the food supply, to cause fatal problems. What a shame that we can’t see giant, flightless swans cradling their cygnets and dabbling for plankton in our current oceans.

There are full articles in New Scientist and in The New York Times. 

Photo Credits

Photo One by – Own work, CC BY-SA 3.0 at,

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