Where do the geese go?

When the seasons change, where do birds go? That question puzzled people for millennia, but it took a long time for us humans to figure out sensible answers. Before you scorn our ancestors, remember how little access they had to accurate information. People could see that the birds had left or the birds had arrived, but they could not know where they had gone. A migrating bird may fly halfway around the world; only in the past few hundred years have we been able to journey that with regularity. Even when sea travel reached the point where humans were circumnavigating the globe, not many seafarers were making rigorously scientific observations – Charles Darwin was the most notable exception – and when they did, how could they tell where individual birds had come from?

Still, we have to give credit to our ancestors, who were at least curious enough to wonder where the birds went in the off-season and who came up with creative explanations. Aristotle decided that birds hibernated during winter. As other species, e.g. bears, do hibernate, his pronouncement was not so unreasonable (Aristotle came up with good theories but didn’t always bother with finding confirmatory examples). Other people thought birds buried themselves in mud for the winter, which might have been an explanation for why they could not be seen hibernating.

My favorite story is the one about barnacle geese turning into barnacles for the winter. Even though the story has long been debunked, the name has stuck, rather like barnacles, to the geese.

We humans (or at least this human) tend to think of barnacles as growing on the hulls of boats. This is because this is how we most easily see the barnacles, as boats and ships bob in the water off some wharf and the barnacles are exposed for our human eyes to see. But barnacles have been living on the planet far longer than people have been building sea-craft, so barnacles have been attaching themselves to other hard surfaces for a very long time. Note that whale bellies also count as hard surfaces. Barnacles, after their larval stages, can’t move about on their own and they must appreciate ships and whale bellies for bringing them through nutrient-rich waters.

Humans believed that barnacle geese turned into barnacles long enough and with sufficient conviction for barnacle geese to be classed as “fish” by parts of the Catholic Church for the devout who were abstaining from meat for Lent, and was apparently acceptable for their old “fish on Friday” requirement. I think it’s strange that people didn’t seem to notice that the barnacles didn’t disappear during the summer. Maybe they believed that they stayed inside the barnacle “eggshells” during the winter and emerged for the summer. How a goose could make itself small enough to squeeze into a barnacle is beyond my comprehension, but there are so many other flaws with the argument I shouldn’t get stuck on that point.

Of course, with the inability to travel great distances, and no ability to identify and track individual birds (crows can tell us humans apart, but most of us have trouble distinguishing individual birds), knowing where a bird had been was almost always impossible, no matter how (un)reasonable the theory.

However, in 1822, in Germany, a stork died – a stork that had been pierced by an arrow that had been shot in Africa. This one case was enough to prove that at least some birds migrate great distances. The unlucky stork’s body (with the African weapon still piercing it) can be found in a museum in Rorstock, Germany.

We humans learned a lot more about bird migration over the years. Rings around bird legs allowed us to be certain of the location of some individual birds, although this method also depended on there being a human finder and the finder being willing to send back the information. Of course, over the years, technology has evolved. Some people, using ultralight aircraft, have been able to accompany geese during their migrations. And now electronic devices are so light and tiny we can do much more. For example, we can accurately observe the paths of the Arctic tern, which avoids winter entirely, going from one polar circle to the other, spending its life in the summer and light.

There’s much more to discuss about bird migration, such as how and why and which species do it; I’ll address some of these issues in other posts. In the meantime, remember that barnacles and barnacle geese have nothing to do with each other in reality.

From Hunters of the Feather:

“Food isn’t always so plentiful,” Mother warned them, as she grabbed a caterpillar off a leaf. “You hatched at the end of spring, when supplies are at their greatest – the insects, the fruit, even the water in the swimming pool. But in winter it’s cold, much colder than any night you have experienced, and often food is scarce. Many of the trees lose their leaves; there is less fruit and the swimming pool is empty. The sun, which is so hot now, offers little warmth, and the days are shorter, the nights longer. Just when you need more food to keep warm, less food is available.”

Lila tried to catch a butterfly, but it flitted away. “What do we crows do then?” she asked.

“Some fly south, where it’s warmer,” said Mother. “That’s why leaders of the local flock are meeting today, to discuss who should go and who should stay. The south is beautiful and warmer in the winter, but migration is hard and not for everyone.”