WHAT THE RESEARCH SAYS

Birds can't see
the glass.

To a bird, a window is sky or a tree.

A large garden-facing window reflecting trees and sky, with rows of small white dots on the outside of the glass — AI-generated image, not a photograph of a real person or place.

Mark the outside
Feeders close up
Plants off the sill
Small changes, fewer strikes

Reflections of greenery and clear views through glass look like open flyway. Bird conservation researchers keep coming back to one fix: give the glass a pattern birds can see, on the outside.

Updated 15 October 2026

THE SHORT ANSWER

Give the glass
a pattern.

Most strikes happen in daylight, at ordinary windows.
Most can be prevented at home.

WHY

Reflections look real

Birds hit glass because they take reflected trees and sky for the real thing, or try to reach greenery they can see through it.

See the numbers

FEEDERS

Closer is safer

UBC advice is to put feeders within half a metre of a window, so birds cannot build up speed before they reach the glass.

How to do it

MARKINGS

Dots, not a hawk

One bird-of-prey sticker does not scare birds away. A pattern with gaps of about 5 cm, on the outside, works.

Check a fix

A QUICK WINDOW CHECK

Which fix
actually works?

Pick a common window fix to see what bird conservation guidance says about it. The bar shows how strongly the guidance backs it.

Based on advice from the University of British Columbia, National Audubon Society and American Bird Conservancy.

Window check

Choose a fixOne hawk stickerStickers on the insideBlinds or curtains closedDots every 5 cm, outsideInsect screen outside

One hawk stickerNot enough

A single decal of an eagle or other bird of prey does not frighten birds away, UBC advice says. Birds simply fly into the bare glass around it.

Stickers on the insideOften unseen

Markings inside the glass can vanish behind strong outside reflections, so guidance says to put them on the outside whenever possible.

Blinds or curtains closedHelps

Audubon lists closing blinds or curtains among the ways to cut reflections and stop birds seeing a clear path through the glass.

Dots every 5 cm, outsideWorks

Patterns spaced about 5 cm apart on the outside of the glass prevent most collisions. White marks you can see from about 3 metres away work well.

Insect screen outsideWorks

Fitting insect screens to the outside of windows is a fix both Audubon and American Bird Conservancy recommend. A screen covers the whole pane.

Sources: UBC Beyond, How to prevent birds from hitting windows; Audubon, Reducing collisions with glass; American Bird Conservancy, Solutions for Homes.

TWO NUMBERS WORTH KNOWING

A huge toll,
close to home.

One estimate of the scale,
one of where it happens.

365–988 million

Birds killed by buildings each year, US

A 2014 review of 23 studies by Smithsonian and US Fish and Wildlife Service scientists estimated between 365 and 988 million birds are killed by building collisions in the US each year.

SCALE · LOSS ET AL. 2014

≈ 44%

Share of deaths at homes

The same study put about 44 percent of that mortality at houses, about 56 percent at low-rise buildings and less than 1 percent at high-rises.

WHERE · LOSS ET AL. 2014

In Canada, an estimated 16 to 42 million birds die each year after hitting building windows, UBC reports. Audubon says that for every victim found, three more typically go unseen.

A hand pressing small white marker dots in a neat grid onto the outside of a window — AI-generated image, not a photograph of a real person or place.

FOUR STEPS TO TRY

Start with the
worst window.

American Bird Conservancy says a small number of problem windows often cause most strikes. Fixing those first can stop almost all of them.

Find the problem glass
Start with windows birds have already hit, big panes and glass doors that reflect greenery or sky, and windows facing feeders or bird baths.
Mark the outside
Draw a pattern with a bar of soap or tempera paint, or use marker tape, keeping gaps to about 5 cm.
Move the feeder
Fix it to the window or within half a metre of it, so birds leaving it are moving slowly.
Move plants off the sill
Indoor greenery seen through the glass can draw birds towards it, so keep plants back from untreated windows.

WHEN IT HAPPENS

Migration, fledglings
and new windows.

American Bird Conservancy says collisions are most frequent during spring and autumn migration, and young birds exploring their area in summer hit glass more often. They happen in winter too, especially near feeders.

Most strikes happen in daylight. Lights left on at night can draw migrating birds into built-up areas, so they meet more glass the next morning. New energy-efficient windows can be more reflective, and people often notice more strikes after replacing them.

A small songbird perched on a clear feeder fixed to the outside of a window pane, with a garden behind — AI-generated image, not a photograph of a real person or place.

Questions

Questions people ask

Why do birds fly into windows?

They see reflections of trees, sky or landscape as real, or try to reach greenery and open space they can see through the glass. Unlike people, they do not learn the cues that tell us glass is there.

Do hawk or eagle stickers work?

Not on their own. UBC advice says research has shown a single bird-of-prey decal does not frighten birds away. A dense pattern across the glass is what works.

How close should markings be?

UBC advice puts the ideal at markers every 5 by 5 centimetres. American Bird Conservancy uses a similar rule of gaps no wider than two inches, and says bigger, white marks work best.

Where should I put my bird feeder?

Either right on the window or within half a metre of it. At that distance birds cannot gather enough speed to be badly hurt if they do hit the glass.

Is it only tall buildings that kill birds?

No. The 2014 US estimate put about 44 percent of building collision deaths at houses and under 1 percent at high-rises, because there are so many homes.

Birds can't see
the glass.