Bird-Safe Glass: What You Need to Know

Bird-friendly windows. Image from the National Park Service's page.

An estimated one billion birds die each year in the United States alone from flying into glass. Simple fixes can greatly reduce collisions: visual markers such as dots or stripes spaced no more than 2 inches apart work best, while one or two decals of birds of prey do not work. The Park Service offers this guidance to help park concessioners, many of whose gift shops sell bird-themed items, and visitors support bird conservation at home.

Why glass kills birds

Birds have trouble seeing glass, an invisible barrier. By day they fly toward reflections that look like sky or plants. At night, lights attract migrating birds and raise their risk of hitting buildings. Homes and buildings under four stories are a major part of the problem: at that height they reflect trees and sky, and they have so many windows that birds find them hard to avoid.

Why it matters

Birds are part of healthy ecosystems, and they help people connect with nature and reduce stress. The U.S. Fish and Wildlife Service estimates there are 96 million birdwatchers in the United States, and their spending and interest in sustainability have a huge economic impact. Treating windows and reducing light pollution protect biodiversity, benefit people and the economy, and save energy. Reducing bird collisions is also part of what the Park Service must do under the Migratory Bird Conservation Executive Order (EO 13186) and its memorandum of understanding with the Fish and Wildlife Service.

What concessioners and visitors can do

Bird-friendly measures can prevent up to 95% of window collisions.

Treat windows by day. Placement and spacing are critical, because birds can fly through surprisingly small gaps. Products recommend spacing pattern elements no more than two inches apart so birds do not try to fly between them. Preventing Bird Collisions with Glass: A Solutions Handbook shows many effective options, and the Fish and Wildlife Service has Bird Collision Reduction Toolkits for different kinds of buildings. Gift shops can sell products that reduce collisions and put information about them next to bird-themed merchandise. Talk with park management about bird-friendly steps for your buildings.

Dim lights by night. Light only where and when needed. Turning off indoor lights at night and closing blinds are easy steps that help birds and other night-active wildlife. The International Dark Sky Association has more on light pollution and its solutions.

Getting started

To find out whether your buildings are a problem, start monitoring. Signs include an unsettling thud or a dusty imprint of a bird on a window. Even a bird that seems only stunned may have injuries it will not recover from. The Fish and Wildlife Service has guidance on setting up a bird–glass collision monitoring program. Once you know whether your windows are a threat, contact your park or the Park Service's avian conservation lead for help with projects to reduce collisions.

Sources

• National Park Service, "Bird Safe Glass: What You Need to Know." https://www.nps.gov/articles/000/bird-safe-glass.htm
• U.S. Fish and Wildlife Service, developing a bird-glass collision monitoring program: https://www.fws.gov/library/collections/developing-bird-glass-collision-monitoring-program
• NPS, make windows safer for birds: https://www.nps.gov/articles/000/make-windows-safer-for-birds.htm; night skies: https://www.nps.gov/articles/000/night-skies.htm