Some birders will argue that the fall migration beats the spring migration hands-down.  Sure, spring songbirds are singing with full throat, dressed in their breeding season finery.  But the spring migration is relatively brief.

The fall migration is much more protracted, spanning early August into December for different species.  Post-breeding dispersal of many species leads to surprising records of vagrant birds.  Storms may also displace migrants.

In recent years, Old World Geese visit New England in small numbers.  A few Pink-footed Geese have graced us with their presence in cow pastures in Yarmouth.  A Barnacle Goose or two visit northeastern North America each fall.  The nearest breeding area for both of these species is Greenland.

We occasionally see a Greater White-fronted Goose.  This widely spread species occurs mostly west of the Mississippi River in North America but also in the Old World, as far west as Greenland.

On October 13, Bill Sheehan hit the goose jackpot in central Aroostook County.  He found six species of geese.  Three species were not surprising: Canada Goose, Cackling Goose (a smaller version of Canada Goose, now recognized as a separate species) and Snow Goose.  But he hit the trifecta of rare geese finding a Barnacle Goose, a Greater White-fronted Goose and a Pink-footed Goose.  A great day!

But Barnacle Goose?  It’s a peculiar name because these geese are vegetarians like other geese and rarely if ever eat intertidal animals.  The explanation for the name provides a good opportunity to think about the methodology of science as we seek to better understand the natural world.

The path leading to our current understanding of bird migration is a circuitous one, with plenty of dead ends.  Like most scientific inquiry, observers build on the observations of those that came before them.  The notion of standing on the shoulders of earlier observers stems from at least the 12th century to a man known only as Bernard of Chartres.  The metaphor is best known from Sir Isaac Newton’s quip, “If I have seen further it is by standing on the shoulders of giants.”

Humans have certainly been aware for millennia that bird abundance changes through the year.  When you depend on birds as part of your diet, failure to pay attention to changes in bird numbers can influence survival.  But where did the birds go?

The notion of migration is implicit in a verse of the Old Testament: “The stork in the heaven knoweth her appointed times; and the turtledove and the crane and the swallow observe the time of their coming.”    In the eighth century BC, Homer wrote that cranes flee from the coming of winter.

A couple of centuries later, Aristotle wrote, “Some creatures can make provision against change without stirring from their ordinary haunts; others migrate as in the case of the crane.”  He also wrote of the migration of pelicans.  So far, so good.  Observers surmised that some birds come and go in response to the changing of the seasons.

Unfortunately, Aristotle also wrote “certain birds (as the kite and swallow) decline the trouble of migration and hide themselves where they are.”  He went to write that some birds hid themselves in hles in the ground, sometimes without their feathers.  Some Greeks also believed in transformation.  In Greece, the European Redstart is a common breeder, migrating to Africa each fall.  The European Robin is a winter visitor to Greece.  Aristotle claimed European Redstarts transformed into European Robins.

In the Middle Ages, Europeans used Aristotle’s mistaken observations to explain the arrival of Barnacle Geese each fall from their high Arctic breeding grounds as a transformation from the stalked, goose-neck barnacles found commonly on floating driftwood.  We’ve come a long way since then but the history of this misstep is perpetuated in the Barnacle Goose’s name.  We’ll continue our exploration of migration next time.

[Originally published on October 25, 2014]