Early on, Interlochen Public Radio did not broadcast 24 hours a day, and Tchaikovsky's June "Barcarolle" was the piece they played at sign-off. Whenever I heard that music, no matter how exciting my novel was, I drifted off to sleep.
I sometimes wish I could still do that. Unfortunately, that dependable sleep trigger — and perhaps my circadian rhythm — isn’t working quite as well as it once did.
But that made me think about the rhythms that govern the rest of the living world.
Birds, mammals, insects and even some plants all carry internal biological clocks. Those "clocks" help regulate daily and seasonal life.
But they don't run on their own. They stay in sync with the world through environmental cues. The most important of those cues is light.
And that is a good thing.
What if wildlife depended mainly on temperature instead? We don’t have to think back very far to remember how unsettled this spring was — warm afternoons followed by sudden cold mornings, as if the season couldn’t quite decide what it wanted to be.
But daylight never hesitates. It changes in a steady, predictable rhythm, day after day, season after season.
Here in the Great Lakes region, midway between the equator and the north pole, the shift is dramatic. Long before we notice it, birds are already measuring it.
Specialized light-sensitive cells in their eyes and brains detect the changing ratio of light to darkness, quietly setting their internal calendars. That signal tells them when to migrate, when to breed, when to molt.
Dawn now arrives long before most of us are awake. Robins are already calling from the treetops while the eastern sky is still pale and gray.
As the days grow longer and the nights shorten, birds respond with precision — when to sing, when to forage, when to rest.
It isn't like a radio station signing off with the same familiar music each night. But in its own way, the changing light of day performs a similar service.
It keeps the natural world on schedule. And for many species, that steady rhythm is not just background — it is survival.
