In the fourth century before the common era, Aristotle wrote a ten volume “History of Animals.” Many of his observations and conclusion were prescient to the work of modern science in the last two hundred years. Others were simply wrong.
Apparently, Aristotle had a particular difficulty with wrapping his mind around the notion that small birds migrate. Instead of migration, he concocted imaginative alternatives to account for the disappearance of some species during the winter, and the appearance of other species.
One theory he proposed was “transmutation,” whereby one species changes into a different species. For example, Aristotle said that the Common Redstart “transmutes” into the similarly sized and shaped European Robin (not related to the American Robin).
The summer nesting Garden Warbler becomes the winter Blackcap. There is enough similarity between the last two species that his conclusion is not too farfetched.
The five species of swallow (including the familiar Barn Swallow) with which Aristotle was familiar leave their breeding grounds in Greece to winter in Africa or southern Asia. Aristotle had no way of knowing this, and, I suspect, such long distance flight by small birds was hard for him to imagine. Therefore, to explain the disappearance of swallows, Aristotle proposed “hibernation.” As winter approaches, the small birds disappear into crevices, holes, and hollows, where they spend the cold months. They reappear with the warm weather, suddenly and in numbers, just like the swallows at Capistrano. They have awakened from months of hibernation.
We have only learned about the remarkable migratory journeys of birds in the last hundred years or so. Many of these journeys are hard to believe. The Blackpoll Warbler flies nonstop 1800 miles over the Atlantic Ocean from the Maritimes and New England to South America. It does so in about 90 hours. Ornithologists studying this warbler suggest that the flight “is equivalent to a human marathon runner completing in 50 consecutive 26-mile (42km) races without consuming any food or water en route and without losing speed from the first to the last leg ... if this tiny bird were burning gasoline instead of body fat, it could boast a fuel consumption rating of about 720,000 miles per gallon.” (Prius, eat your heart out.)
A female Whimbrel (a medium sized shorebird with a long curved bill) was fitted with a satellite transmitter in May of this year. By mid-August she had been tracked from Virginia to Alaska to the Hudson Bay, more than 8,000 miles. On August 10 she left the Hudson Bay. On August 14 she landed on St. Croix, Virgin Islands, having traveled 3,500 miles in 100 hours. That’s an average speed of 35 miles per hour.
The Arctic Tern breeds in the Arctic. It winters in the Antarctic. The round-trip migratory route is about 25,000 miles.
With satellite tracking, researchers have learned that a Wandering Albatross with a chick in the nest, may go on a foraging voyage that covers a wandering route of 10,000 miles. This is not even a migration from breeding grounds to wintering grounds. This is just to eat, and presumably bring food to its chick.
The Bar-tailed Godwit breeds in Alaska. It winters in New Zealand. A female with a satellite transmitter “left Alaska on August 30 and arrived in New Zealand eight days later after a nonstop oceanic crossing measuring 7,250 miles ....” That’s an average speed of about 38 miles per hour, over open ocean with no resting places. She slept on the wing.
With our modern scientific sophistication, we laugh at Aristotle’s notion that birds hibernate. However, the reality of bird migration is harder for the human mind to grasp than the notion of hibernation. If we did not have hard scientific evidence, we would dismiss each of these extraordinary flights as beyond all reasonable possibility. We can’t walk five miles on the Appalachian Trail without consuming handfuls of high energy gorp, but a four ounce shorebird, the Ruddy Turnstone, can fly 125 miles and only burn one gram of fat. For that matter, typing at my desk is so strenuous, I just went downstairs to get a piece of left-over Halloween chocolate in order to keep my energy level up.
If any of you laugh at the notion that birds hibernate, you have little concept of what is reasonable, sensible, logical, and believable. It is far easier to believe, as Aristotle proposed and as all intelligent people for two millenia agreed, that some birds hibernate during the winter. Easier to believe that, than some of the incredible flights and migrations that some birds actually make.
At least, it is easier to believe Aristotle until we are confronted with the empirical scientific evidence. And let’s not laugh at Aristotle. I am quite sure that were he reincarnated today, he would acknowledge his error in the face of the facts ... which cannot be said of everyone, judging by some of the crazy notions that are accepted today as fact (and my mind is made up).
I return briefly to Aristotle’s other alternative to considering the migration of small birds: transmutation. When I compare an American Goldfinch in breeding plumage with an American Goldfinch in winter plumage, I see a pure bright yellow bird with a few stunning black highlights and a dull, nondescript, olive-drab bird. They are so different that a novice could easily think them two different birds. I don’t know if there are any European species that undergo a similar dramatic change in plumage, but I can understand how Aristotle might postulate transmutation.
As to birds hibernating ... some do. Aristotle was not completely wrong. More anon.
Good birding.
Note: Most of the research for this columns was done with The Migration of Birds by Janice Hughes (Firefly Books, 2009). The author tells the fascinating history and science of migration. It is a rarity in the book word - a glossy, small-sized coffee table book that demands reading.
The Lake Champlain - Hudson River valley is a known flyway for the scoters. Scoters occasionally show up on the set-back ponds along the Connecticut River, but this tiny pond in Newfane seems very unusual. Then again, Newfane is one of the loveliest and most picturesque towns in New England, and lots of tourists stop. Why not a scoter?
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