Buildings kill millions of birds. Here's how to reduce the toll

These birds were killed by flying into a set of surveyed buildings in Washington DC in 2013. USGS Bee Inventory and Monitoring Lab/Flickr

Norman Day, Swinburne University of Technology

As high-rise cities grow upwards and outwards, increasing numbers of birds die by crashing into glass buildings each year. And of course many others break beaks, wings and legs or suffer other physical harm. But we can help eradicate the danger by good design.

Most research into building-related bird deaths has been done in the United States and Canada, where cities such as Toronto and New York City are located on bird migration paths. In New York City alone, the death toll from flying into buildings is about 200,000 birds a year.

Across the US and Canada, bird populations have shrunk by about 3 billion since 1970. The causes include loss of habitat and urbanisation, pesticides and the effects of global warming, which reduces food sources.

An estimated 365 million to 1 billion birds die each year from “unnatural” causes like building collisions in the US. The greatest bird killer in the US remains the estimated 60-100 million free-range cats that kill up to 4 billion birds a year. Australia is thought to have up to 6 million feral cats.


Read more: For whom the bell tolls: cats kill more than a million Australian birds every day


But rampant global urbanisation is putting the reliance on glass buildings front-of-stage as an “unnatural” cause of bird deaths, and the problem is growing exponentially.

In the line of flight

Most birds fly at around 30-50km/h, with falcons capable of up to 200km/h. When migrating, birds generally spend five to six hours flying at a height of 150 metres, sometimes much higher.

And that’s where the problems start with high-rise buildings. Most of them are much taller than the height at which birds fly. In Melbourne, for example, Australia 108 is 316 metres, Eureka 300 metres, Aurora 270 metres and Rialto 251 metres. The list is growing as the city expands vertically.

The paradigm of high-rise gothams, New York City, has hundreds of skyscrapers, most with fully glass, reflective walls. One World Trade is 541 metres high, the 1931 Empire State is 381 metres (although not all glass) and even the city’s 100th-highest building, 712 Fifth Avenue, is 198 metres.

To add to the problems of this forest of glass the city requires buildings to provide rooftop green places. These attract roosting birds, which then launch off inside the canyons of reflective glass walls – often mistaking these for open sky or trees reflected from behind.

Reflections of trees and sky lure birds into flying straight into buildings. Frank L Junior/Shutterstock

A problem of lighting and reflections

Most cities today contain predominantly glass buildings – about 60% of the external wall surface. These buildings do not rely on visible frames, as in the past, and have very limited or no openable windows (for human safety reasons). They are fully air-conditioned, of course.


Read more: Glass skyscrapers: a great environmental folly that could have been avoided


Birds cannot recognise daylight reflections and glass does not appear to them to be solid. If it is clear they see it as the image beyond the glass. They can also be caught in building cul-de-sac courtyards – open spaces with closed ends are traps.

At night, the problem is light from buildings, which may disorientate birds. Birds are drawn to lights at night. Glass walls then simply act as targets.

Some species send out flight calls that may lure other birds to their death.

White-throated Sparrows collected in a University of Michigan-led study of birds killed by flying into buildings lit up at night in Chicago and Cleveland. Roger Hart, University of Michigan/Futurity, CC BY

Read more: Want to save millions of migratory birds? Turn off your outdoor lights in spring and fall


We can make buildings safer for birds

Architectural elements like awnings, screens, grilles, shutters and verandas deter birds from hitting buildings. Opaque glass also provides a warning.

Birds see ultraviolet light, which humans cannot. Some manufacturers are now developing glass with patterns using a mixed UV wavelength range that alerts birds but has no effect on human sight.

New York City recently passed a bird-friendly law requiring all new buildings and building alterations (at least under 23 metres tall, where most fly) be designed so birds can recognise glass. Windows must be “fritted” using applied labels, dots, stripes and so on.

The search is on for various other ways of warning birds of the dangers of glass walls and windows.

Combinations of methods are being used to scare or warn away birds from flying into glass walls. These range from dummy hawks (a natural enemy) and actual falcons and hawks, which scare birds, to balloons (like those used during the London Blitz in the second world war), scary noises and gas cannons … even other dead birds.

Researchers are using lasers to produce light ray disturbance in cities especially at night and on dark days.

Noise can be effective, although birds do acclimatise if the noises are produced full-time. However, noise used as a “sonic net” can effectively drown out bird chatter and that interference forces them to move on looking for quietness. The technology has been used at airports, for example.

A zen curtain developed in Brisbane has worked at the University of Queensland. This approach uses an open curtain of ropes strung on the side of buildings. These flutter in the breeze, making patterns and shadows on glass, which birds don’t like.

These zen curtains can also be used to make windows on a house safer for birds. However, such a device would take some doing for the huge structures of a metropolis.

More common, and best adopted at the design phase of a building, is to mark window glass so birds can see it. Just as we etch images on glass doors to alert people, we can apply a label or decal to a window as a warning to birds. Even using interior blinds semi-open will deter birds.

Birds make cities friendlier as part of the shared environment. We have a responsibility to provide safe flying and security from the effects of human habitation and construction, and we know how to achieve that.


This article has been updated to correct the figure for the estimated number of birds killed by the cats in the US to “up to 4 billion”, not 4 million.

Norman Day, Lecturer in Architecture, Practice and Design, Swinburne University of Technology

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Taking care of dogs with dementia: Kerry and Kenzo’s story


Kerry Mcmyler lives in Lancashire in the UK.  She’s had her dog Kenzo, a Labrador Collie cross for 15 years–ever since he was a puppy. She says he chose her from a litter of nine, barging past all of them to go to her.

When she moved away some six years ago, her parents took responsibility for Kenzo who was then about 10.  Then a couple of years ago, he started barking in the evening, and showed other signs of anxiety and restlessness. The family also noticed a pattern where these behaviours would start in the late afternoon and continue until midnight.

While researching Kenzo’s symptoms online, Kerry came across information about Sundowner’s syndrome in dogs, where dementia-like symptoms worsen at night. She says it all came together for her then, especially when the vet later confirmed it.

Sadly, Kerry’s father passed away last year, and it’s been an emotional time for her and her family. Kenzo was dependent on her dad for routine and connection, and she feels one of the triggers for his behaviour could be pining for her father.

Kerry is 44 and a healthcare Science Associate Practitioner in Microbiology (Infectious Diseases) with the Royal Lancaster Infirmary.

She and her partner moved back to take take care of her mum and Kenzo, and I caught up with her during a very busy time.  We spoke via email.

What was your reaction to the diagnosis? What went through your mind?

How myself, my mum and my partner Sarah were going to cope with just losing dad. Was he just missing him? Was he grieving? I gave him an old jumper of dad’s but he wasn’t interested. He shows all the tick boxes of Canine Cognitive Decline (CCD) except the incontinence. 

What treatment –that you know about–is available in the UK for dementia in dogs?

Unsure at present. We have him on a calming pill called Xanax and he also has arthritis so he has 1/2 paracetamol twice daily. We have tried CBD (Cannibas oil) too which did help for a while but he has run out of this at present.  It does calm the barking down but not the restlessness. 

You say that at the beginning of Kenzo’s dementia, he was living with your parents who had a routine for him. But now this has changed because of your dad’s sad passing. Can I ask, how bonded was Kenzo to your father?

Very much so, he was the person that took him for walks. So his routine has had to change. I now take him when I arrive home from work. The shocking factor for me was mum was quite socially phobic having arthritis herself and relied on dad to help her get about.   However, whilst I was at work a few months ago, she decided to walk him on her own. It was a huge turning point for her [in] regaining her confidence.  Kenzo walked with her slowly and did not pull which was so lovely.


Image: Kerry Mcmyler

You’re the primary carer for your mum, and I wonder if you could describe what that means to you—being a carer.

It is a responsibility of selfless love. After dad passed away, my partner Sarah and I gave up our jobs 320 miles away.  I withdrew from my [university education]. I was one year off finishing my biomedical degree. However, sadly this hospital cannot fund or allow me time off to complete it. And now I have had a change of heart about where my life is heading to after much reflection.

I left my job of nine years in microbiology, and Sarah [left hers] in helping the elderly in rehabilitation. We moved in with mum so she did not have to sell the house, and to help her with daily tasks, bills and to give her company. I know we have done the right thing and it has set us all in a new direction. As an only child, I love my mum dearly and I want to make her time on this earth as special as it can be and make as many memories as I can with the time she has left. 


What’s the hardest thing about watching dementia in Kenzo?

His confusion, his age, his restlessness; falling off the sofa when he does not judge it correctly. We have said if he becomes incontinent we would put him to sleep. It is too much for mum to go through at 78 years old, having just lost dad too. I don’t want to lose her too. It would be the kindest thing to do however, for now, we are coping the best we can. 

How are you coping wth the demands of Kenzo’s care ?

It is tiring [to] after a 9-hour day…walk him [and] be up till midnight with his constant barking, crying and restlessness.   We try to reassure him but it is simply draining when you still have a daily life to live and chores to do. During the day he is fine, however, I work so I don’t really see the quiet side of him.  He is great with mum during the day. It is when I come home after 5 pm this starts. There has been quite a lot of tears and a huge relief when he is finally asleep. 

Kenzo in the snow
Image: K erry Mcmyler

How would you describe your relationship with him now?

I love him to bits.  He still greets me dutifully when I walk through the door of an evening but not of a morning. His eyesight is failing so I have to bend down to have eye contact with him but if I ask for a kiss sometimes I still get one off him. For that split-second, everything is back to normal. He recognises me, how can I possibly put him to sleep. Just another month…let’s see how we go…and the cycle continues. 

Kenzo and friends
Image: Kerry Mcmyler

You say that you will “know when it’s time”. It must be the hardest moment.  What will tell you that, and how do you imagine that moment in the future when you will have to say goodbye to Kenzo?

Heartbreakingly when he stops being responsive. Stops eating, drinking, or [becomes] incontinent. I would not want him to be in constant pain with his arthritis so if his back legs keep failing him there has to be a point where we end his suffering and do the kindest last thing a human can do. But we don’t say goodbye it is always “until we meet again”   


Image: Kerry Mcmyler