Tag Archives: dark skies

Dim the Lights for Birds at Night

Ines Nedelcovic
Katherine Wychulis 

We’re all looking forward to spring migration when warblers and other migrating birds return to Northern Virginia to breed or visit on their way north. Peak songbird migration in our area is mid-April to mid-May. Now is a good time to take extra steps to greet our migrants by making our homes and neighborhoods a little safer for them, helping them avoid window collisions and exhaustion.

The American Bird Conservancy estimates that up to 1 billion North American birds die each year due to collisions with windows. (ABC) Some species greatly affected by window collisions include the Black-throated Blue Warbler, Ovenbird, Ruby-throated Hummingbird and our star singer, the Wood Thrush. (Klem, Solid Air, pp. 40-41) The toll during migration can be high because about 70 percent of North America’s bird species are migrants. (Audubon Talk to Arlington Joint Advisory Committee at 18:10) 

Illustration reprinted with permission from the Cornell Lab of Ornithology. Learn more and see when bird migration is happening in your area, with forecasts and real-time bird migration maps at Birdcast.info.

Birds crash into windows because they perceive the glass as air, and see reflections of vegetation, or they see through the glass to indoor plants. The highest collision rates occur in large areas of continuous glass like office buildings and large residential windows.

Lights are another part of our built environment causing bird mortality, particularly the external lighting concentrated in urban and suburban areas and along highways.

So how do outside lights harm birds? Eighty percent of our migratory birds migrate at night, using the star map and the moon to navigate. Bright lights can dampen or mimic moonlight and starlight, confusing the birds. Disoriented or dazzled birds can lose their way or stall. The confusion exhausts them in the middle of an already arduous journey and can trap them in hazardous city environments. (Audubon Talk, at 18:10)  

Voluntary “Lights Out” programs are helping to reduce the harm in cities like Chicago, the #1 most light-dangerous city for migratory birds. (Audubon Talk, at 31:00) Effective techniques include taking light “breaks,” down-shielding lights, and minimizing blue light. 

So, how can we reduce the impact of our buildings on birds? 

  • Turn lights off when leaving a room, and cover windows with blinds, shades, or other coverings.
  • Install insect screens on windows, or apply decals or stickers providing visible patterns on the outside of the window. Most birds will avoid glass with vertical and horizontal stripes or markings spaced 2” apart. The stripes should be at least ⅛” wide. Dots work if they are at least ¼” in diameter. ASNV’s website has a very helpful video on how to prevent window collisions. ABC and Klem, pp. 150-151 are also useful sources.
  • Place bird feeders either within 3 feet of windows or more than 30 feet away. (Klem, p. 108)
  • Turn off outside lights at night if possible. As an alternative, use yellow LED lights less than 3,000 kelvins which are less disorienting and deadly to beneficial insects, and for any security lights, use motion-sensor lights. (Audubon Talk, 41:00-43:50)
  • Report bird-window collisions resulting in a dead or live bird on iNaturalist, joining the bird window collisions project.
  • Share these tips with your neighborhood via an HOA, landlord or NextDoor and support local “Lights Out” initiatives.

Originally published by the Audubon Society of Northern Virginia.