Caring for a bird that strikes a window

You hear a thud, and by the time you get to the glass there is a smudge on the outside and a bird on the patio. What you do in the next few minutes decides whether it flies off or dies of shock, and most people get it wrong by helping too much.

The scale of this is larger than it feels from one back garden. The Bird Conservation Network, a coalition of bird conservation groups, has long put the annual North American toll from window collisions above 100 million. Later work by researchers at the Smithsonian Migratory Bird Center placed United States building collisions higher still, in a range of several hundred million birds a year, with the majority happening at houses and low buildings rather than at towers. Ordinary residential glass, one or two birds at a time, is where most of it occurs.

Why birds fly into glass

They are not being careless. Glass presents two problems that no bird evolved to solve.

The first is reflection. A window facing a tree, a hedge or open sky shows the bird a continuation of the habitat it is already flying through, and at speed there is nothing in that image to contradict. The stronger the daylight outside and the darker the room behind the glass, the better the mirror.

The second is transparency. Where a bird can see through a corner window to sky on the far side, or through a patio slider to houseplants and a bright kitchen window beyond, it reads a flight path. Both problems get worse in spring and fall migration and around dawn, when light levels and traffic are both high.

Repeated tapping is a different thing entirely. A bird that hits the same pane again and again through the breeding season, then perches, then hits it again, is fighting its own reflection over territory. That bird is not injured and a box will not help it. Break the reflection on the outside and the behavior stops.

What to do in the first few minutes

Watch before you touch. A large share of birds that strike are stunned rather than hurt, and given quiet they collect themselves and go. Stand back far enough that you are not part of the stress and give it five minutes.

The most useful thing you can do in those five minutes is remove the other dangers. Bring the dog in. Get the cat inside and keep it there. Keep children at a distance. A stunned bird on open ground in Phoenix has a second problem beyond the predators, which is the ground itself: paving in summer will kill a bird that cannot move off it. If it is sitting in full sun on hot concrete, that is the one case where immediate handling beats waiting, and moving it a short distance into deep shade nearby is enough.

Handling a stunned bird without making it worse

If five minutes pass and the bird is still down, upright but not moving off, you can contain it while it recovers.

• Wear gloves or use a light towel. This is for the bird’s sake as much as yours.
• Use a cardboard box with a lid, large enough that the wings are not pressed against the sides, with holes punched in the top and a folded towel or a paper towel in the bottom. Avoid a wire cage, which damages feathers.
• Cup the bird gently, wings held against its body, and set it down inside. Close the lid.
• Put the box somewhere dark, quiet and moderate in temperature, indoors, away from an air conditioning vent and away from the noise of the house.
• Offer nothing. No food, no water, no eyedropper. A stunned bird cannot swallow properly and liquid put in its bill can drown it. A dish of water in the box is a drowning risk for the same reason.
• Leave it closed. Do not lift the lid every few minutes to check. Handling and being looked at by a large mammal are both read as being caught by a predator, and shock kills more collision birds than the impact does.

After thirty minutes to an hour, carry the closed box outside, away from the window it hit, set it down, open it and step well back. A recovered bird will leave within a minute or two. Never open the box indoors, because a panicking bird in a room finds the nearest window and does the whole thing again.

When to leave a bird alone

Not every bird on the ground has hit anything. In spring, a fledgling that is fully feathered, hopping about and calling is doing what fledglings do, and its parents are nearby watching you. Picking it up is a kidnapping, not a rescue.

A bird that flies off immediately after a strike does not need to be found. If it made it into a tree under its own power it is better off there than in your box.

When to call a wildlife rehabilitator

Some things are beyond first aid, and the honest answer is to hand the bird to somebody trained. Call a rehabilitator if you see bleeding, a wing that hangs or sits at a different angle from the other, a head tilt or circling, an eye that looks damaged, feet that cannot grip, convulsions, or simply no recovery after a couple of hours in the box.

In Arizona, the Game and Fish Department maintains a list of wildlife rehabilitators who hold the state and federal permits this work requires, and Liberty Wildlife in Phoenix takes in injured native birds. Call ahead before you drive anywhere, because intake hours and species vary.

There is also a legal side that catches people out. Nearly all native North American birds are protected under the federal Migratory Bird Treaty Act, and keeping one in your possession while you nurse it back to health is not permitted, however good the intention. Containment for an hour while a stunned bird recovers is fine. Keeping an injured bird for a week is not, and a permitted rehabilitator will do more for it in a day than a kitchen box will do in seven.

Prevention that works, and what does not

All of this happens on the outside face of the glass, which is where the reflection lives. That single fact rules out most of what gets sold for the purpose. Decals stuck on the inside of a window are behind the mirror and the bird never sees them.

Spacing is the other thing people get wrong. A bird will attempt any gap it thinks it can fit through, so one hawk silhouette in the middle of a large lite simply gives it two clear halves to aim at. Markings need to be close enough together to read as a barrier, which in practice means gaps no wider than about two inches in either direction.

What holds up in the field:

• Exterior insect screens or solar screens across the whole opening. This is the most reliable fix there is, it works on every pane it covers, and in Phoenix it cuts afternoon heat gain at the same time, so it earns its cost twice.
• Vertical cords hung on the outside a few inches apart, which birds see and read as solid while you barely notice them from inside.
• Exterior patterned film, dot arrays or paint markers applied to the outer surface at tight spacing.
• Moving bird feeders and baths either within about three feet of the glass, so a startled bird cannot build up speed, or more than thirty feet away.
• Closing blinds on the see-through path in a corner room, or on a slider that lines up with a bright window opposite.

Ultrasonic gadgets and single stickers do not survive contact with the evidence. If a particular window has killed birds before, it will keep doing it until the outside of that window looks different.

Checking the glass afterwards

Most strikes leave nothing but a dust print, the powder down from the bird’s feathers, which washes off. Glass is harder than people assume in this situation and a small songbird against a modern window is not a serious impact.

Damage does happen, though, and it depends on what the pane is. Tempered glass, which is what you have in patio doors and most large lites near a floor, resists a strike well but has no middle ground when it does fail: it breaks completely, into small pieces, and it cannot be patched. Laminated glass holds together on its plastic interlayer. Ordinary annealed glass in an older single pane window is the one that chips or cracks, and a heavy bird such as a dove or a grackle at speed can do it.

Once the bird is settled, look at the pane properly. Run a fingernail over the outside face where the smudge is, since a shallow chip catches. Check the edges of the lite where it meets the frame, because that is where a crack starts and where a chip matters most. Look along the glass at a low angle in daylight rather than straight on. Press lightly at the center of an old putty or bead glazed pane to feel whether it has gone loose in the frame.

One thing to watch over the following weeks: an impact can break the seal on an insulated unit without visibly damaging the glass, and the first sign of that is haze between the panes on a humid morning. If it appears, the unit has failed and the glass gets swapped while the frame stays, which is the foggy window repair job rather than a new window.

Where there is real damage, be aware that resin injection is a windshield process and does not apply to a household window. A chipped or cracked pane in a house is replaced. In a sound frame that means new glass into the frame you already have, which is straightforward window repair rather than a rebuild. Full window replacement only comes into it when the frame is finished, and a bird strike is seldom the thing that finishes a frame. If the glass looks fine, it almost certainly is fine, and you can stop looking at it.

If a pane did take damage

Superior Replacement Windows has handled residential glass across the valley since 2010, family owned, working a 50 mile radius from 4202 E Elwood St #21, Phoenix, AZ 85040. Send a photograph of the chip or crack, or call (602) 777-3717, Monday to Friday, 7:30am to 5:00pm, and we will tell you whether it needs doing at all before anyone comes out. More on what we cover is on our residential glass page.