Small Birds. Long Migration.

“You know the hummingbirds disappear when you start to see the sandhill cranes migrating.” I was sure this elderly gentleman was going to start telling me about how hummingbirds migrate by hitching rides on the backs of sandhill cranes, but he didn’t. Instead, the look in his eyes and slight smirk clearly told me this was a bit of humor.

I suspect many among us have heard some folklore about how small birds manage to migrate long distances. Most of our songbirds migrate south for the winter, of course. A few species stay, but not very many. It seems that during the spring and fall migrations we often wonder just how they do it. Not all of the birds will make it to their winter destination, but the majority of them will.

Of course they do not all fly non-stop to their wintering grounds. Many species will make occasional stops to refuel. And even though some birds may lose body weight during migration, they appear to make it to their destination without becoming exhausted in the process.

Fat is the fuel that gets most birds through their migration. But all that hard work, burning all those fat calories during long distance flights, would be expected to result in considerable lose of body water. One would expect that the birds would become severely dehydrated, but that apparently does not happen. So what is going on here?

Scientists at the University of Western Ontario recently published a study in the prestigious journal Science that has shed some light on how birds balance their energy needs with their need to stay hydrated during long migrations. Studying Swainson’s thrushes in controlled environments, they discovered that these birds get their energy, not only from fats, but also proteins. The breakdown of proteins to fuel their flight results in more water given off in muscle cells than would be produced using fat for fuel. So using some amount of protein in addition to fats as their source of energy would help maintain their state of hydration.

There are still some birds migrating through our area. Take the time to enjoy these fall flights. Even though scientists are solving some of the mysteries of migration, it always seems to fill us with a sense of awe and wonder.

Chuck Lura

Natural North Dakota is supported by NDSU Central Grasslands Research Extension Center and Minot State University-Bottineau, and by the members of Prairie Public. Thanks to Sunny 101.9 in Bottineau for their recording services.