What Happens to the Birds that Survive a Window Collision?

It’s a distressing reality that millions of birds continue to tragically die in Canada every year due to collisions with glass. Most of the birds that hit windows die on impact or soon after due to their injuries. But some birds simply appear to be stunned. Will these birds be ok?

White-throated Sparrow – Photo: S. Scharf

Many people think that a bird that manages to fly away after a collision with glass just needed time to shake it off. But you would never expect someone who had a high-speed collision with a stationary object (like a car accident) to simply ‘shake it off’. You would probably take them to the hospital to be checked out by a professional! That’s why it’s often the best course of action to take a bird that has hit your window to your local wildlife rehabilitation facility, even if it just looks stunned.

In the wild, a bird needs to be in the best shape possible. If it can’t fly strongly or has other impairments, it may become an easy snack for a hungry wild animal or someone’s cat. On top of this, many birds that hit windows during migration may still need to fly hundreds to thousands of kilometers to reach their final destination, which is no easy task even for a healthy bird.

Even window collision survivors that are feisty and outwardly look unhurt may have severe injuries. Injuries can also develop or worsen without medical treatment. These birds often require anti-inflammatories to reduce swelling in their brain, medicated eye drops for painful abrasions on their eyes from the collision (called corneal ulcers), and pain medication for the bruises or lacerations on their bodies. Some will have fractured bones or beaks which require time to heal. Many birds must stay in care for several days or weeks as bones repair, bruises heal, and muscles get stronger.

After recovering from their injuries and once they are deemed strong enough to keep up with the demands of life in the wild, these birds are released to continue their migratory journeys.

But what happens then? Are these rehabilitated birds as good as new and able to survive and migrate normally like their companions?

The truth is, we don’t know yet, but we are close to finding out. Scientists from Powdermill Nature Reserve have partnered with FLAP Canada and other organizations in a multi-year study to answer this important question.

As you might imagine, there are major logistical challenges with chasing around a tiny migratory songbird, especially as they fly hundreds of kilometers in a single night. Luckily, new technologies including lightweight tracking devices are allowing scientists to follow the movements of individual birds over these vast distances.

The Motus Wildlife Tracking System is an array of special towers across North America (and the world) that allow scientists to remotely track the movements of migratory animals. Researchers fit birds with tiny, lightweight backpacks called nanotags. These nanotags are so light that even a Black-throated Blue Warbler, which itself weighs slightly more than a toonie, can carry one without being slowed down.

Black-throated Blue Warbler with a nanotag – Photo: Bethany Thurber

As the bird moves around, the nanotags emit a unique pulse around every 10 seconds that allows the towers to identify the bird should it fly within range. The detection is then logged in a centralized database. Using the Motus System, scientists can follow birds that have survived and recovered from a window collision to find out if they are surviving in the wild and having a normal migration.  

This past fall, trained FLAP volunteers and researchers in Toronto equipped birds that had survived a window collision with a nanotag. For every window collision victim, they also tagged another healthy bird of the same species. This way, scientists can compare birds that are likely on a similar migration route and schedule to see just how different things are for the window collision victims.

One of the birds that the researchers tagged this fall was a White-throated Sparrow. The bird had hit a window on the second story of a glass building on the York University campus and was stranded on a glass overhang. A FLAP volunteer found the bird, and the rescue involved a panicked but successful search around campus for a ladder tall enough to reach and safely contain the bird. The White-throated Sparrow then spent the next 9 days in care at Toronto Wildlife Centre, recovering from bruising and swelling on one shoulder, eye ulcers, and a fracture on the very tip of its beak.

This White-throated Sparrow recovered from a window collision and was later released with a nanotag to track its movements

Dedicated FLAP volunteers work tirelessly during migration seasons to locate and rescue window collision survivors in need of medical attention. Some of these ‘FLAP birds’ have joined the White-throated Sparrow and continue their journey sporting a fancy nanotag. These avian ambassadors will provide us with a rare glimpse of their life after a collision. If birds continue to experience a handicap from a window collision even after rehabilitation, glass may pose an even greater risk to birds than we had previously imagined.