By Jeffrey Lu
The time draws near for the return of many of Minnesota’s insects and birds. That animals disappear for the winter has been common knowledge since the dawn of humankind, but few people ever stop to consider what an amazing feat migration is. Twice a year, some animals travel hundreds or even thousands of miles without the aid of vehicles, maps or directions. In order to make such journeys, animals developed some astounding adaptations.
Considering how challenging migration is, why even risk it at all? The answer boils down to resources like food. Studies have found that birds which raise their young in the north raise larger clutches of eggs than their near relatives who stay year-round in the tropics.
How do migratory animals manage their marathon voyages? Before the journey begins, animals’ bodies must prepare extensively. The monarch butterflies which fly south to Michoacan, Mexico live for nine months instead of the usual two to six weeks, pause breeding until the spring, and modify their muscle composition for better stamina. And they pack on so much fat for the journey and time in Mexico that they increase their weight by up to 40 percent. That is like a 150-pound person putting on another 60!
During the journey, animals can use methods such as soaring on the wind at specific altitudes and flying in ‘V’ formations to save effort. The lead bird in the V disturbs the air as it flies, reducing air resistance so the following birds use up to 30 percent less energy. These adaptations enable some astounding feats of stamina. Our state bird, the Common Loon, has been recorded covering 670 miles in a single 24-hour period!
Navigation is another important component of migration, and animals handle it with multiple methods, which are poorly understood and still being studied by scientists. The start time is determined by the hours of daylight as it changes over the seasons. Once enroute, animals can use the relative position of celestial bodies like the sun, moon and stars like mariners of yore. Even more amazingly, many animals seem to have an internal compass, orientating themselves with the earth’s natural magnetic fields.
While animals with longer life spans are also able to follow their elders and then their own memories of landmarks and smells, shorter-lived animals like monarch butterflies and green darners solely rely on their instincts as different generations make legs of the journey. In fact, monarch butterflies go through so many generations a summer that the butterflies who return to Mexico are the great grandchildren of the monarchs who overwintered the previous year.
While migrating animals are beautifully adapted to the challenges of long-distance travel, they live in a human altered world of shrinking habitats and pollution. Fortunately, there are many ways you can help our migrating friends. You can plant pollinator gardens and native plants to provide birds and insects habitat. Reducing pesticide use can help preserve existing habitat.[JJ1] Keeping cats indoors is best for migrating birds and cats, as cats hunt billions of birds every year. Turning off lights at night helps migrating birds as well because the glow of cities throws off the celestial navigation of birds. You can help during the day as well by making your windows visible to birds with dots, patterns, or screens to prevent bird strikes.
Participating in citizen science programs like Cornell’s Ornithology program also helps migrators by enabling scientists to understand their needs and humanity’s impact on them. Finally, you can tell your representatives to enact policies which lessen human’s impact on migrating animals and support efforts to preserve habitat critical to migrating birds. We at Kroening Nature Center hope you welcome our migratory friends back to Minnesota![JJ2]
This article was written using information from the Cornell Lab of Ornithology, the Smithsonian Institute, the US Geological Survey, the Library of Congress, articles written by M. Hallworth et al, and W. Wiltschko et al, and the National Wildlife Federation.
Join us for upcoming programs at Kroening Nature Center! Browse and register all programs at minneapolisparks.org/activities-events/nature-activities or call 612-370-4844.
Highlighted programs in March at Kroening Nature Center:
Bird Watching: Beginner Basics · Saturday, March 11, 9-10:30 a.m. Free, for ages 8+ (activity #136202) Learn the basics of birding through the park with a naturalist. No prior birding experience necessary. Binoculars provided.
Hike: Mississippi River Eagles · Saturday, March 18, 11 a.m.-noon. Free, for ages 8+ (activity #136239) Eagles are returning to nesting sites along the river! Learn about our national bird and look for these majestic predators while walking the park trails.
Animal Tracking · Saturday, March 25, 10-11:30 a.m. Free, for ages 55+ (activity #140565) Join Bill Kass, a certified member of the MN Tracking Club, to learn how to identify animals that make North Mississippi Regional Park their home. This class will consist of a classroom introduction followed by exploration along the river and through the woods in search of clues.