The impacts of window strike on our native birds

Department of Conservation —  17/02/2018

By Kelly Hancock, Community Ranger

Cleaning windows must be one of the most dreaded household tasks. If you manage to keep your windows sparkling clean, well done – you’re doing better than me!

But those clean kitchen windows present a hazard for our feathered friends. Each year, hundreds of native birds die or suffer terrible injuries after colliding with windows.

Mark left after a kererū window strike.

Kererū window strike

Jessica McCutchan is a vet at Wildbase Hospital. She paints a pretty graphic picture of window strike injury in birds.

“It most often results in multiple soft tissue injuries and fractures to the bones around the chest area. Typical injuries include crop rupture, bleeding around the heart and fractures or dislocations of the coracoid, scapula, keel and clavicle bones. Usually, there are fractures to multiple bones, which can then puncture not only surrounding muscle but also organs such as lungs and heart.”

An injured kererū as a result of window strike. Image: Wildbase Hospital.

An injured kererū as a result of window strike. Image: Wildbase Hospital

Window strike often occurs when birds are startled while feeding or resting. They may also perceive a clear line of flight reflected in your window, or from one window to another within your house.

Young birds learning to fly are especially vulnerable. Kererū, tūī, morepork/ruru, black back gulls/tarāpuka and harrier hawks are common victims.

Annotated patient X-ray from Wildbase Hospital

Annotated patient X-ray from Wildbase Hospital

In the unfortunate event that your house windows are involved in an avian accident, call the DOC Hotline (0800 368 468) for advice on arranging treatment for injured birds.

In the lower North Island, victims of window strike are usually treated at Wildbase Hospital.

Annotated patient X-ray from Wildbase Hospital

Annotated patient X-ray from Wildbase Hospital

“All birds that come to Wildbase Hospital receive a full physical examination, stabilization and, depending on findings, go under an anaesthetic to take full body radiographs and blood tests,” says Dr McCutchan. “With these results a full assessment of the prognosis for recovery and release to the wild can be made.”

Sadly, the severity of trauma caused by a window strike impact is huge, and extremely painful. They cannot escape predators as they are unable to fly. Prevention is the best medicine.

How to prevent window strikes

Aside from not cleaning your windows, one of the easiest and most effective ways to prevent bird strike is the use of ‘Window Alert’ decals. These are stickers that help deter birds by reflecting UV light. The translucent transfers make parts of the window opaque to birds, but are barely visible to humans.

Packs of window decals can be purchased from Bird Rescue Trust. Proceeds from sales help to fund bird rehabilitation centres.

If you have a bird feeder in your garden, make sure it is less than 1 metre or more than 10 metres from a window. Feeding birds are easily frightened and then take wild, evasive flight. If your feeder is close to the window, birds are likely to fly away from the house.

Special thanks to Carina Svensson, Wildlife Technician and Jessica McCutchan, Veterinarian. Construction of the Central Energy Trust Wildbase Recovery Centre is well underway, with the facilities expected to be operational in mid 2018. To find out how you can support it, see

2 responses to The impacts of window strike on our native birds

    gray limbrick 25/02/2018 at 11:01 am

    not all birds are seriously injured by window strike.Out of around 15 woodies that have hit
    my windows only one has died.IT actually is dependent on the angle the bird hits at that
    will determine the severity of the strike.

    Anton Petre 18/02/2018 at 3:38 pm

    The window alert decals are very effective and not offensive on the windows. You can also buy them online…..just Google “Window Alert”