Every winter readers contact me about various aspects of bird migration and it seems even more so than usual this year.

Some are curious about where a particular species goes for the winter and how they find their way there. Many are reporting seeing birds that shouldn’t be here this time of year. Bluebirds are the most notorious for this. They’re supposed to be farther south but a few tough it out here in southern Michigan every winter.  About a month ago I had a half dozen hanging around my shop in blustery weather for over a week.

Also back in mid January with over a foot of snow on the ground a local reader reported a flock of a dozen robins in his yard. More geese, ducks, great blue herons and kingfishers are electing to forego migration than ever before. We can’t blame global warming for there hasn’t been any significant winter temperature increase in years. To my knowledge there’s no plausible explanation.

In fact, bird migration remains one of nature’s greatest mysteries.  Particularly baffling to science is how migrating birds navigate with such precision. This has been extensively studied nigh-on forever and we still have little but theorized guesses. To complicate the issue, it appears different species utilize different methods. We’re sure geese at least in part actually learn migratory routes from their elders and use landmarks such as mountains, rivers and lakes. However, this is unique to just a few species. Some birds such as homing pigeons just seem to have an innate and unfailing sense of direction no matter the circumstances. Most birds appear to have some degree of this. Birds have been transported from their natural grounds to areas far out of their normal range, even to other continents, and released. Many quickly found their way back and continued their normal migration patterns.

Most birds appear to have complex compass and mapping systems that rely on various factors. Studies indicate many daytime migrators learn to use the sun for direction as they are growing up.  It doesn’t seem to be so much the sun’s ever changing position from day to day and minute to minute but its vertical relationship to the horizon. Some of these birds have been raised in cages with mirrors to make the sun appear in a different position. When released into the real world they were totally screwed up and could hardly find the ground with both feet. Similarly, when birds were raised allowing them to only see the morning sun they could navigate fine in the mornings but were clueless in the afternoons.

Many birds migrate only at night. Studies raising such birds in planetariums indicate they learn to navigate at least in part by the stars. They don’t appear to memorize the whole galaxy, but rather its rotation around a base star, such as the North Star. Birds reared in a planetarium with normal star rotation around the North Star had no directional problems. Those raised with the star rotation altered to move around some different star the birds used that star for navigation, which, of course, when they were released really messed them up.

Studies show magnetic fields also have a navigational role with many birds. When birds are under the strong, natural urge to migrate and are restrained in enclosures they actually sit facing and walk in the direction they should be migrating. Natural magnetic fields run north and south from pole to pole, the way most birds migrate. Such birds placed in enclosures where the magnetic field direction was altered with magnets re-oriented to the altered direction.

But all these findings barely scratch the surface. It may explain how a bird can find its way in a general direction. However, it lends no insight as to how the bird knows where in this wide world to head in such a direction or how many hundreds or thousands of miles to go in order to land on that little quarter acre spot it calls home. Despite all our efforts we still have no idea.

Carpe diem.

Larry Lyons writes a weekly outdoor column for Leader Publications. He can be reached at larrylyons@verizon.net