The Beauty of Pleistocene Swans (Cygnus buccinator)

Photo from google images of a trumpetor swan.

No animal symbolizes the beauty of the Pleistocene more than the trumpetor swan (Cygnus buccinator).  I suppose we can consider it a stroke of good fortune that this species didn’t become extinct with the spectacular megafauna of that bygone era.  Contemporary efforts to protect the bird and help re-expand its range have even been moderately successful.

Modern range map of the trumpetor swan.  It occurred as far south as South Carolina during colonial times.  During the Pleistocene there was likely a sizeable population of this species in the southeast where it is completely absent today.  Fossils of this species have been recovered from northern Alabama and Florida.  Overhunting by men extirpated this species from much of its former range.

Before European settlement of North America trumpetor swans were more common and widespread, migrating as far south as South Carolina during severe winters.  But during the Pleistocene they ranged even further south.  Bell Cave in northern Alabama and several sites in Florida have yielded fossils of this bird.  Ice Ages provided ideal habitat for this species.

Audubon mentions that trumpetor swans prefer a moderate climate.  Ice Age summers in the south were generally cooler and winters were still moderate, so swans would have had a favorable climate in this region then.  It seems likely that Pleistocene trumpetor swans bred and nested on the abundant glacial lakes near the boundaries of the great ice sheets. Then during winter they didn’t have far to migrate because the distance between glacial lakes and favorable wintering habitat in the south was much less than the distances they have to travel today.  Perhaps a segment of the population remained and nested in the south year round, much like modern day sandhill cranes of which some migrate and some are permanent residents.

Map of the Laurentide glacier.   During the LGM swans didn’t have far to migrate between summer nesting grounds near glacial lakes and winter habitat in the south.  Some segments of the population probably lived year round in the south.

Swans inhabit ponds and small lakes with aquatic plants growing on the bottom upon which they feed. Extensive beaver ponds and marshes, and oxbow lakes were the kinds of abundant habitat in the south available to the big birds then.  Swans nest and take cover on beaver dams, muskrat lodges, and islands where they’re relatively safe from mammalian predators. If hungry enough, mammalian carnivores will expend the energy to swim and search for food in wetlands, but it’s not their first choice when looking for an easy meal.  During stadials, islands on braided rivers were common, giving swans lots of favorable habitat.  This wouldn’t have kept swans safe from eagles, however.

Photo from google images of a bald eagle killing a swan.  Eagles of several kinds were common during the Pleistocene.

Grinnell’s crested eagles, golden eagles, and bald eagles were capable of hunting and killing swans during the Pleistocene.  But swan defense mechanisms were adequate enough to maintain substantial populations.  Swans weigh up to 30 pounds and a blow from their wing is powerful enough to break human bone.   They can also flee by submerging and swimming for some distance.  They’re most vulnerable to eagles and human hunters when in flight.

Swans have an interesting method of feeding.  While they swim on the water, they lower their long necks to reach the aquatic plants growing on the bottom.  Because they have longer necks than geese, they can outcompete them for food by eliminating all the fodder within a goose’s reach.  Swans also graze grass on land; and they eat snails, reptiles, and small mammals.

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2 Responses to “The Beauty of Pleistocene Swans (Cygnus buccinator)”

  1. James Robert Smith Says:

    I missed out on photographing trumpeter swans last year in Yellowstone. I saw some in the Yellowstone Rive and in the Snake River in the Tetons one day and figured I get a better chance the following days. Alas, I never saw another one. That’ll teach me!

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