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Migration is among the most astonishing and challenging stages in any bird’s life–a metabolically demanding journey riddled with perils, from hazardous weather and food shortages to human-caused impacts like light pollution. Fully 80% of our terrestrial migrants in North America migrate at night–including warblers, thrushes, sparrows, kinglets, siskins and grosbeaks. Migrating at night provides a number of benefits, including: avoiding daytime predators, preserving daylight hours for foraging, taking advantage of a less turbulent atmosphere, and using the stars to navigate!
Unfortunately, birds are increasingly exposed to light pollution along their migratory pathways from unshielded and overly bright fixtures on our homes, streets, buildings, billboards, and empty parking lots. All of these sources accumulate to produce “sky glow”— the hazy dome of light over our cities that drowns out the stars that birds use to navigate, pulling them off course and into lit areas where they can become entrapped in light, hit buildings directly, or face other urban hazards like cats and cars.
Thankfully, there are tools to help us reduce light pollution during peak migration season. Though peak songbird migration spans more than three months in both spring and fall, most of the birds that fly over Oregon will pass over during a one month period in each season, from mid-April to mid-May and again between mid-September to mid-October. Researchers at Colorado State University’s AeroEco laboratory are using radar technology to track movements of birds on migration, and they post user-friendly alerts for peak movement nights on their website (https://aeroecolab.com/). Red, orange and yellow alerts signal large movements of birds, with red alerts representing the highest forecasts relative to total peak historic bird migration. Audubon chapters across Oregon have been coordinating efforts to help broadcast these alerts so that people know when it is most important to turn off any unnecessary outdoor lights to help keep birds aloft. Lane County Audubon often posts these on our Facebook page.
Bear in mind–light pollution doesn’t just impact migrating birds. It impacts entire ecosystems, including nesting birds, fish, mammals, amphibians, invertebrates and plants as well as human health, safety and culture. Completely darkening our cities during migration isn’t practical or safe, but we can take actions to ensure that our lighting is better by design. We can minimize unnecessary light at night, and keep the light that we need on the ground where it’s useful rather than sending it up into the sky where it isn’t. It’s a sound practice in the age of climate change, and it saves money, saves birds, protects human health and affords us a better view of the stars! Audubon is working to raise awareness about the importance of this natural resource that is slipping away, little by little.
There are simple things that we can all do at home to help save our night skies:
- Watch for Lights Out Alerts both spring and fall and turn off your unnecessary lighting!
- Check out CSU’s Aero Eco Lab for alerts in various cities and statewide
- Turn lights off when you’re not using them
- Make sure that all your lights are shielded and aimed down
- Switch to motion sensors (or motion sensor bulbs)
- Use bulbs only as bright as you need!
- Choose warm light bulbs (yellower>whiter)!
- Close blinds/shades at night during migration seasons
- Help advocate for good lighting Standards in your city
How do radar ornithologists track birds?
Radar technology—Radio Detection and Ranging— uses radio waves to detect objects, and came into practical use in the 1940s to detect enemy aircraft during WWII. But there was noise in the system when radio waves bounced off of objects like storm fronts, which gave rise to its use forecasting weather. Another form of noise—pale wisps on radar called ghosts or angels— remained a mystery until the 1950s when they were successfully identified as migrant passerines—a breakthrough that evolved into the remarkable ability to track bird migration!
There are 143 Doppler radar stations around the continental US, and these stations help ornithologists keep a watchful eye on migrants moving under a cloak of darkness. Birds have unique signatures on radar maps that set them apart from storms, insects, and bats, so scientists at both CSU’s AeroEco Lab and Cornell University are able to monitor migrant bird activity and translate this information into Lights Out Alerts that help us mobilize our conservation campaigns locally.
Credit to Kyle Horton at CSU AeroEco Lab:
For additional ideas: Ways to Help Migratory BirdsWays to Help Migratory Birds