Migration has evolved so wildlife can remain active year-round. Obviously, this is only part of the reason, because many species of animals do not migrate at all and remains in an area year-round. Some species, however, have solved the problem of coping with extreme environmental conditions by hibernating or slumbering inside cozy dens throughout the coldest of winter days.
While many species of birds find no reason at all to vacate Minnesota (some stay in Minnesota and other northern-tier states throughout the winter), some species of birds actually migrate to Minnesota to spend the winter, not leave it. The snow bunting is a good example of a bird that migrates south to Minnesota for our “tropical” winters. Come spring, the snow bunting returns to the Arctic Circle to breed and nest.
The reason that many birds migrate is often food-driven. Ducks and geese would have no problem spending the entire winter right here if food and water were readily available. And some actually do remain here if conditions are right. But just how they migrate is an even more intriguing question.
It is believed that migration is possible amongst species through a combination of factors. With some birds, navigation is accomplished through learned experiences across known routes, over known landmarks, to known destinations.
Still, too, the stars and sun play important and vital roles for those species of birds migrating during the night and day. And, stranger yet, the geomagnetic fields of the earth provide some species a means of orientation. Even the sense of smell helps some birds, like pigeons, literally smell their way home.
I recall one March night about 30 years ago when I took a walk under the light of a full moon. I happened to have my binoculars with me because I intended to look at the surface of the moon at its crater-pocked surface. As I stood looking at the moon through the optics, an unexpected sight delighted me.
At first, I thought it was an isolated event. Rather, it was a major migration of neo-tropical birds taking place right before my eyes. For minutes on end, I witnessed silhouettes of birds flying across the face of the illuminated moon. It was the first time I had ever seen such an event. Try this yourself on a springtime, moonlit night with a pair of binoculars. You’ll be surprised by what you see.
But perhaps one of the most awe-inspiring migratory spectacles I have ever observed occurred in the Prairie Pothole Region of North Dakota during early spring. Tens of thousands of ducks and geese were flying everywhere I could see.
On that particular "bluebird" day with scarcely a hint of a breeze, endless flocks of migrating geese and ducks steamed northward. This great event was the result of a several-day layover because of foul weather that kept many birds grounded. But on this day, when the weather broke, it was as though feathered floodgates were opened and a mass exodus ensued.
Some birds migrate impossible distances across vast stretches of ocean without stopping because landing would be certain death. The bar-tailed godwit, for example, is one such migratory champion. Depending on the subspecies, some of these godwits are capable of flying nonstop some 7,000 miles.
If not for the species’ physiological abilities that adds incredible stores of fat to their bodies, a 50% increase in muscle mass, and organs that actually shrink during migration, these migratory miracles would not be possible. Moreover, their special brains allow them to alternate a “sleep” pattern from one side of the brain to the other while they fly, thus resting each side of the brain at different times.
Avian migration is as fascinating to study as it is to observe. At this very moment, migrant birds are flying northward, mostly at night to take advantage of fewer predators, cooler temperatures and easier flying conditions. And soon enough more will arrive to our backyard feeders as we get out and enjoy the great outdoors.
Blane Klemek is a Minnesota DNR wildlife manager. He can be reached at firstname.lastname@example.org.