Lights Out, Minnetonka!

Brilliantly colored trees, falling leaves and flocks of migratory birds are classic autumn events – but what triggers those phenomena? A key factor is shorter day length. At Minnetonka’s latitude (almost 45 degrees north of the equator), we lose about 2.3 minutes of sunlight per day after June’s summer solstice. That adds up quickly. By the end of September, nearly four hours of daylight have shifted to darkness.

Shorter autumn days lead to cooler nights, prompting plants to ease off on leaf growth and seed production in favor of root-building. Animals use autumn’s fading bounty to fatten up for migration, hibernation or other cold-weather survival strategies.

People also respond to autumn’s cues: We turn on lights, indoors and out, to extend the shorter days. Artificial lighting is convenient and reassuring for us – but it poses a lot of risks for wildlife. 

Blinded by the light

On any autumn night, there may be millions of birds in the sky over the United States. Some fly thousands of feet above the Earth; others keep close to the ground. Dark skies offer a clear view of the stars and moon, which nocturnal migrants use to navigate.

What happens when migratory birds fly through towns and cities, like those lit up on this NASA satellite map of the U.S.? The Moon and starlight fade under the glare of artificial lighting. Fall and spring migrants may become disoriented or temporarily blinded by the light. The American Bird Conservancy estimates that up to a billion birds die during migration each year, many after colliding with windows they couldn’t see.

City lights, like those shown in this night-bright image of the Twin Cities metro, aren't just a problem during migration. Light can affect a wide range of animals year-round. Artificial lighting drowns out the flashing displays fireflies use to attract mates. Moths are notoriously drawn to light and may expend their energy swarming instead of breeding, feeding or pollinating plants. Lights also expose wildlife to predators – including outdoor cats – and may act like a barrier to helpful hunters, such as bats that help control mosquito populations.

Less light

Small changes make a big difference for wildlife – and the benefits can be immediate. What’s more, reduced lighting will save money on your utility bill and reduce emissions related to energy production. Here are a few tips:

• As much as possible, reduce artificial lighting outdoors. If you’re concerned about home safety or want to deter deer and other nocturnal wildlife from your yard, consider installing a motion-sensitive lighting system. Check city code section 300.28 for details about ordinance related to exterior lighting.
• Make sure exterior lights are shielded and carefully oriented to reduce glare and light spillage across landscapes that could be used by wildlife.
• Turn off interior lights by midnight, or pull curtains during peak migration. For fall migration, that’s Aug. 15 through Oct. 31; spring migration peaks between mid-March and late May.
• Encourage neighbors, businesses and others to reduce artificial lighting.

Visit Audubon Minnesota's Lights Out program to learn more and take their pledge.

More from Natural Resources

• Buckthorn Workshops - Wednesday, Sept. 13 OR Thursday, Oct. 5, 6:30–8:30 p.m. at Minnetonka Community Center, 14600 Minnetonka Blvd. Learn tips that will save you time and money as you tackle this invasive plant on your property. Advance registration is required online, or call 952-988-8400.
• Building Healthy Soils workshop - Thursday, September 28, 6-8 p.m. at Ridgedale Library. Join entomologist and soil health evaluator, Dr. Ann Marie Journey, to learn about urban soil ecology, and learn what actions you can take to build healthier soils at home. Advance registration is required through Ridgedale Library.
• Urban Soils: Challenges and Opportunities walkshop - Saturday, October 7, 1-3 p.m. at Minnetonka Community Center (14600 Minnetonka Blvd.) Soil is the key to healthy plant diversity, which in turn feeds pollinators, wildlife and people. But what exactly is soil, and how does urban development impact it? Join Dr. Ann Marie Journey for a walk around Minnetonka’s Civic Center Park to see how soil varies between woodlands, wetlands and lawns. Along the way, you’ll learn ways to improve the soil in your yard. Note: This walkshop will be held outdoors, following paved trails (with some inclines) to various sites throughout the park. Please dress for the day’s forecast weather. Advance registration is required online, or call 952-988-8400.
• Volunteer with us! Check our website for dates, locations and registration.
• Native Plant Sale. Fall is a great time for planting! Visit the sale page to learn what’s offered and how Minnetonka residents can get a $20 discount.
• Residential Buckthorn Pick-up. If you’re removing invasive buckthorn on your property this year, there are several options to dispose of the debris:
  • Haul it to the brush drop-off site at Minnetonka Public Works. Visit our website for hours, locations and details.
  • Hire a contractor to chip the debris on site, then use it as mulch.
  • Apply for residential buckthorn pick-up through our Resilient Minnetonka program.
  • Remember: City ordinance requires that cut buckthorn and other yard debris be stored out of public view until disposal. Debris may not be dumped on public lands or wetland areas.