The Natural Enquirer: A rainy day walk
A soft tinkling sound sparkles across the marsh. A light rain falls steadily from a heavy gray sky. No wind ruffles the water’s silvery gray surface; the rain drops are soft and light so that each makes a small round jewel-like ring where it strikes.
The tinkling of rain falling gently on still water is one of the most soothing sounds I know. On a rainy day few other people are out and clouds and rain seem to settle around me, shutting out the rest of the world. It is one of the most rewarding times for a quiet walk in a forest or park. You might not expect to see much wildlife during “bad” weather, but in fact rainy days can be excellent for wildlife observation. Some birds seem to positively enjoy rain; robins and brown thrashers, for example, take shower baths, standing in the open and ruffling their feathers until they are quite wet.
This morning as I look over the marsh, three red-tailed hawks circle in the wet air, a Canada goose sits placidly on the water with its long neck up like a mast, and several mallards swim nearby. A wood duck flies in from trees along the marsh edge with a loud, sharp cry of “whooo-eeek.” Blending with the sound of raindrops is the steady call of dozens of wood frogs. Farther along the trail a pair of wood ducks rises from a small brush covered pool deep in the woods; a minute later a second pair follows. At least a dozen robins and a single flicker search for worms on a recently burned area.
Although many mammals are less active than birds in wet weather, squirrels and rabbits may be out, especially if rain continues for several days. Today there is a gentle, windless rain. Yesterday, rain came in a series of thunderstorms. In such severe weather, with high winds, lightning, and hail possible, all animals must try to find at least minimal shelter and most sit tight until the worst is over. Even so, in a lull between heavy bursts of rain the season’s first tree swallows flew over in a small flock, and during another break a rough legged hawk circled and hovered overhead.
For the wild things changing weather-what we call bad weather-is part of life, and they must continue to forage, protect their nests, care for the their young and do all the other things that maintain their lives. Certainly severe storms take their toll, just as severe cold and snow exact a price in winter, but each species is adapted to the weather of its home range, so that life goes on.
Rain is of course essential as it brings the moisture that is the life blood of all ecosystems. In northern Wisconsin we live in a temperate climate, even though it doesn’t always seem so, with precipitation distributed fairly evenly through the year and no regular periods of extreme drought or torrential rains. We also live in the mid-section of the continent, far from the oceans, and changeable weather is the rule. While average conditions are fairly mild, short spells of weather can be extreme. Even harsh storms, damaging as they may be, are an essential part of our world and can be beautiful to watch.
While animals must adapt to weather and climate it would be presumptuously anthropomorphic to say they understand that rain brings life. Rain is simply part of their world, and they know no other. But we know, and one more joy of a rainy day walk is to feel that life giving process at work.
Why are rainbows round, and often double?
The most common rainbows form when sunlight enters raindrops. The drops act like prisms and disperse the sun’s light into the familiar spectrum of colors: red, orange, yellow, green, blue, indigo and violet. Rainbows are round by necessity because of the geometry involved in seeing them. You see a rainbow when you have the sun to your back and the raindrops are in clouds in front of you. Rays of light come over your head from behind you, enter raindrops, get dispersed into colors, bounce off the backside of raindrops and come down into your eyes. The eye must intercept the beam of light coming from the drops at a particular angle in order to see the colors. A visible rainbow will form only if the drops are in the right place, so that there is a certain angle between the sun, the drops and your eyes. The angle must be a constant angle, and the only geometry that keeps that angle constant involves a circle.
You only see the part of the circle that is above the horizon. If you imagine where the rest of the circle is, you will see that you can draw a straight line from the sun through your head to the middle of the circle that the rainbow is part of. It sounds poetic, but it is scientifically true that no two people see the same rainbow. If three people are looking at a rainbow, each is at the right angle for that particular rainbow.
Occasionally people will see a second rainbow outside the first rainbow, a bigger circle. The colors in that second rainbow are reversed. The second rainbow is also typically fainter. What happens is that the light follows a similar path, but the light beam bounces twice Inside the raindrops. The two reflections have two effects: the order of the colors is flipped, and on each reflection, light is lost, scattered out of the drop, making the second rainbow fainter and less often observable.
To test all this yourself, in warm weather, you can make a rainbow with a garden hose set to a fine spray and the sun at the right point behind you.
Peter Dring is a retired nature biologist and phenologist who lives in the Land ‘O Lakes area. To comment on this story, visit the “Outdoors” section of StarJournalNOW.com.