Are glass towers strictly for (or against) the birds?

Here’s another reason to be dubious about all those skyscrapers clad with reflective glass: they're the second biggest killer of birdlife after habitat destruction

Alan Davies — Editor of The Urbanist

Alan Davies

Editor of The Urbanist

Toronto's reflective towers are lethal for migratory birds (source: NYT)

Toronto has a lot of glass-sheathed skyscrapers, but they have a sinister side. Reflective buildings are a serious hazard for birdlife and Toronto is in the top rank of the world’s most lethal cities.

According to this report in the New York Times, Casualties of Toronto’s urban skies, at least one million birds – but possibly as many as nine million – die from collisions with glass-clad skyscrapers in the city every year (H/T Matthew Kahn).

Toronto not only has a lot of crystalline towers forming a barrier along the north western shore, it’s also on “several migratory flight paths:

So many birds hit the glass towers of Canada’s most populous city that volunteers scour the ground of the financial district for them in the predawn darkness each morning. They carry paper bags and butterfly nets to rescue injured birds from the impending stampede of pedestrian feet or, all too often, to pick up the bodies of dead ones.

The founder of the brilliantly named bird rescue group FLAP (Fatal Light Awareness Program), Michael Mesure, says he once recovered 500 dead birds in a single morning. He took the NYT reporter to a particularly deadly building on the eastern edge of Toronto’s financial district and pointed to:

a gaggle of sea gulls sitting in trees across the street from an office building. They were waiting, he said, to dine on the smaller birds maimed or killed by the building.

The building has a glass facade that disorients birds by reflecting the surrounding trees. Perceiving the reflection as habitat, birds zoom at it full throttle without regard for the danger.

The victims are largely songbirds. Perhaps because of familiarity, the urbanites of the bird world, like house sparrows, pigeons and gulls, are much less prone to crashing into glass…

FLAP is taking legal action against the owners of two of the deadliest buildings. There’s a technical solution that involves applying a visibly patterned film over windows, especially on the lower levels where trees are reflected.

A German company, Ornilux, markets a glass with a pattern in the UV spectrum visible to birds but not humans. The company says bird strikes are the second largest cause of avian mortality after habitat destruction.

It is the reflective and transparent characteristics of glass that create a dangerous situation for birds. They see sky and landscape reflected by or on the other side of a window; the glass is not perceived as a barrier. To prevent these collisions, glass must be made visible to birds.

Mr Mesure says the danger to birds from reflective buildings is rarely considered by developers and architects. Complex or faceted reflective facades appear to be especially problematic.

I’ve no idea how significant bird strikes on buildings are in Australia (although I know Melbourne’s Western Treatment Plant is a destination for northern hemisphere birds), but there appear to be straightforward solutions. Creative designers could make them a positive.

Perhaps they could even look beyond the standard reflective facades to other forms (whatever happened to brise-soleil?).

The NYT points to a dilemma – one of the deadliest buildings in Toronto has historical value. It’s the last built work designed by Mies van der Rohe.

The urban smarts of sparrows, gulls and pigeons is intriguing. Do these species have attributes that enable them to adapt readily to the wiles of humans (like reflective buildings)? Or were generations of less wily ones simply wiped out over the last few decades (another form of adaptation, of course)?

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12 thoughts on “Are glass towers strictly for (or against) the birds?

  1. Alan Davies

    IkaInk #11:

    Here’s another report on the same research from Scientific American.

    As noted in my last para above, the interesting question is: is it learning or is it selection? I’d go the latter.

  2. IkaInk

    A very old topic I know, but I just read this and it reminded me of this post:

  3. Dylan Nicholson

    Well I suppose I have a suspicion attitudes and priorities might change that somewhat in the next 30 or 40 years. Call me an eternal optimist…

  4. Alan Davies

    The international carbon price is currently circa $10 per tonne. And cases where “government could just buy back the land” would be very, very limited.

  5. Dylan Nicholson

    Also Boscombe, the idea of more small towns/cities appeals to me too (mainly because I’ve seen how well it works in Europe), but I don’t see how to make it happen in Australia – there’s plenty of incentives to encourage people out of big cities already but they don’t seem to be doing much. Seems far more realistic to try to establish and encourage multiple business districts in existing large cities, instead of having such a concentration in the CBD, which is a process that has been going on for the last few years already, and is surely attracting a more population growth than our smaller towns and cities. But even say, Box Hill in Melbourne, which has the potential to become a significant “secondary BD” doesn’t have any high-rise apartments yet.

  6. Dylan Nicholson

    Carbon credits could easily be a decent incentive. And in some cases governments could just buy back the land.

  7. Alan Davies

    Dylan Nicholson #5:

    Dylan, maybe we can agree though that land converted to residential use is already degraded.

    Unfortunately I don’t have a biologist handy, but farming land is generally pretty short on habitat. Horticulturalists in particular have a long history of conflict with birds.

    Good luck with getting farmland converted back to its 1770 state. Even if residential expansion is contained, there’s not a lot of incentive for landowners to revegetate.

  8. Dylan Nicholson

    Alan, I’m sure any biologist would tell you that the land supported far more wildlife before it was converted into suburbia, and if we were able to allow farmland to return to its natural state, it would do so again.

  9. boscombe

    Skyscrapers and endless miles of suburbs are both extremes we’d probably be better off without. My previous job was in a big modern building and the air-conditioning was always somehow not right. I know at one stage they decided to save money by taking in less fresh air and recycling the air already heated or cooled.

    It’s like the frog being slowly cooked … I didn’t realise the effect of it ’till I moved to my current job in an old building and started to feel much better. Many days, like today, I don’t turn on the air-conditioner or the light because I don’t need them – I have the door open and my desk in near a window.

    Instead of going ever up and up or out and out, we need to create more towns and small cities.

  10. Alan Davies

    IkaInk #1, Dylan Nicholson #2:

    We need advice from an evolutionary biologist to answer that one!

    Dylan, re your point about glass towers vs suburbia, in most cases in Australia the land that’s converted to residential subdivisions was cleared a long time ago for farming. Conversely, some suburban subdivisions (like mine) are thick with habitat and food sources and consequently they’re thick with bird life.

  11. Dylan Nicholson

    Very much doubt natural selective forces would have acted THAT quickly – we’ve only had significant numbers of mostly glass sheathed buildings for 100 years at most. It’s not surprising to me that birds that are born and “grow up” around the city are able to learn how to detect that glass buildings can’t be flown through, even if they have to learn the hard way (presumably a fair number of impacts are survivable).

    And while I’m all for minimizing the harm humans unnecessarily do to other species, this one frankly doesn’t strike me as Homo Sapiens’ greatest crime against nature. The space saved by building and living in glass towers as opposed to turning bushland into suburbia and farmland surely saves FAR more lives.

  12. IkaInk

    My bet is on the latter for urban birds. They adapt because the ones that don’t notice the glass die pretty quickly. In the long term I’m sure migratory birds would do the same, but that doesn’t exactly mean the problem should be ignored in the meantime. Populations could be devastated to the point that there is some serious disruption in eco systems before they could start to recover with a more skyscraper aware population.

    As for Mies van der Rohe’s final building: I’ve always been of the idea that any historical element that is within a city will only be worth preserving if it can be done in a way that allows it to adapt to new uses and newly recognised design problems, i.e. there is no point preserving old buildings if it means turning them into “museum pieces” and keeping things exactly as they are. This is why we’ve got accessible ramps built on historical buildings, why old factories are retrofitted into up-market apartment blocks, etc. In this instance putting a film over the glass, or replacing the glass with something the birds can see seems like a bit of a no brainer.

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