We awoke this morning to dozens of northern rough winged swallows feasting on insects over the cattails. Like many other birds, they form groups after the breeding season and prior to departing on their fall migration to far away places, which for rough winged swallows means Mexico or Central America.
Seasonal migration is an awesome subject and is applicable to birds, insects, fish and mammals. It’s a behavior as old as life itself, and movements can vary from as little as a few hundred meters for the blue grouse to a mind boggling 44,000 zig zagging miles for the Arctic tern.
There are mysteries at work, and specialized adaptations for navigation are always being discovered. The magnetic poles play a prominent role, but exactly how they are processed in animals is still in question. Magnetism alone does not explain how an oriole flies thousands of miles before returning to our backyard to rest on a deck rail where nine months earlier was a jelly feeder. This level of accuracy indicates a detailed memory, or an extremely refined GPS system.
If we can be baffled and humbled by a tiny hummingbird making its way to Central America and back each year, wrapping our heads around butterflies and dragonflies that require multiple generations to complete their annual migratory trek is beyond comprehension. Indigenous peoples believed that medicine men were born with the memory of what their predecessors had learned. The concept must apply to migrating insects as well, some sort of message in their genetic code that details their migratory routes and destinations with impeccable accuracy.
Lake Superior measures 160 miles north to south. Monarch butterflies migrating south from Canada manage to flutter nonstop across the open expanse. It's an impressive enough feat if the migrants set a straight line route, which they don't. Instead, at a certain location they make an abrupt eastward turn and stay that course to a prescribed point where they again turn south, adding unnecessary distance. The belief among scientists is that Superior once contained a mountain of ice, or some sort of obstruction of such height that the insects could not fly over but instead flew around, and the memory has not been lost to time.
Native Americans would often have seasonal migrations between summer and winter hunting grounds, and in the US today about a million people head to Florida to lay out the winter while others seek the dry mild air of the desert southwest. But migration applied to humans generally refers to movement in only one direction, a dispersal often spurred by force or desperation. Worldwide, a person is being unwillingly uprooted every two seconds.
Unless we are direct descendants of native peoples and have remained within our ancestral borders, we all have a migration or two in our histories. Over the decades a disproportionate number of us have migrated to coastlines or mountainous regions. We jockey for prime locations in beautiful natural settings such as lakeshores, then moan about aquatic weeds and mosquitoes, beavers that eat our yard trees and deer that eat our hostas. We build on the coasts then fear mudslides and earthquakes and hurricanes. We speckle homes in mountainous areas then expect fire suppression where uncontrolled wildfires had managed forest ecosystems for centuries. We move from cities and bring demand for Starbucks and fine restaurants and nightlife. Entrepreneurs respond, more folks move in, and soon congestion fills the quaint mountain or seaside town. In every migration there are hopes and heartaches, losses and gains, assurances and uncertainties, but with none comes an iron clad guarantee.
Think of the risks associated with seasonal migration, the extreme outputs of energy. A bird, having fought hard to establish and defend its nesting territory, abandons it, assuring a repeated effort the following season. If it's nest fails there might be a second attempt, with fledglings too weak to make the arduous cross country trip. What great advantage to sit tight, keep the home fires burning, and bring reproduction to strong completion.
Food is a driving motivation. There are no flowers in winter for nectar seeking hummingbirds, no plankton in cooling waters for feeding whales, no browse for elk in the high country. Yet some of the great blue herons in our region move south while others stay to endure the cold, banking on finding food not locked in ice. There are questions unanswered.
Climate change is affecting every life form. Plants are moving north, and along with them food sources for associated species. Everything alive is a candidate for redistribution, and the impact on human cultures, food supplies, and migration behaviors is phenomenal.
It’s August and the great seasonal spectacle has commenced. Weather radar picks up the activity at night, masses of birds streaming southward. Shorebirds, especially, are well underway. Most of the orioles have left the feeders, as have the grosbeaks. Their work here is done, and the shortening days have flipped an internal switch which cannot be ignored.
A mysterious and finely tuned seasonal mechanism for so many things wild, a hope-filled and sometimes final alternative for millions of people, migration lies intricately woven in the quest for survival.
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