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Green glass, blue sky April 7, 2008

Posted by eyegillian in Canada, diversity, environment, life, nature, urban.
Tags: , , , , , , , , , , , ,

photo by Gillian Barfoot (aka Seeing Is)

The spring migration has started here in Canada. All manner of birds — either planning to stay for the summer, or heading to a more northern destination — can be spotted by those with time and the inclination. What’s that twitter? Did you see a flash of yellow up in the tree? Crane your neck, pull out the binoculars, sift through descriptions in your favourite bird book…

And if you live in Toronto, head downtown where birdwatching is made easier by the presence of a pile of tall glass-walled buildings. All you have to do is scout around the bottom of the office towers to find a wide selection of birds, all lying still and easily identified.

Since 1993, volunteers with Toronto’s FLAP (Fatal Light Awareness Program) have counted 40,940 birds killed in collisions with office towers. Research shows that glass windows kill more birds — estimated at between 100 million and 900 million — per year than any other cause.

Lights Out Toronto logo

One problem is the office towers which leave windows brightly lit after dark. Night migrants are confused by the lights, since they use the stars and moon as navigational tools. They either flutter around the light until they drop from exhaustion, or fly into the illuminated object. These bright towers cause more confusion on rainy or foggy nights when the birds fly at a lower altutude. The Lights Out Toronto program has been developed to encourage business owners to reduce their night lighting, especially near windows.

Another problem is the fact that glass walls and windows tend to reflect the surrounding environment. If it reflects their natural habitat, the trees, shrubs or sky where they would normally take refuge, chances are good they’ll fly towards it. Some buildings place trees or large plants just inside their windows, attracting birds to their death. In other situations, glass on both sides of a building creates the illusion of an unobstructed corridor. Birds will gather momentum as they prepare to fly through the perceived passageway.

The increased interest in creating green buildings may spell trouble for birds, as passive solar heating emphasizes windows, lots of windows. The highly efficient “low-e glass” — low-emittance glass coated with metal-oxide to keep the summer heat out and the winter heat in — has a dangerously mirror-like quality. Even the green roofs reflected on surrounding buildings can lure birds into walls.

This realization has led to a number of solutions and innovations as homeowners and architects try to make their buildings safer for birds.

A porch is enclosed in bird-safe mesh at the Ford Calumet Environmental Center in ChicagoSeveral innovative designs featured in Architectural Record earlier this year feature buildings with “visual noise” — patterns that make birds realize the glass windows are an obstruction. Small openings and mesh coverings (as used to surround the wide porch in the photo on the right) also help deter birds.

One of the most intriguing experiments is using ultraviolet coating on glass. Although ultraviolet light is invisible to the human eye, birds see it. The question is still unanswered, however, as to whether ultraviolet coating deters birds.

city squares

Another interesting treatment is called “fritted” glass, as seen in the photo at left, which shows a window installed on a University of Montreal residence building. The small patterns on the glass, along with the green shading, help make the window more visible to birds.

Other ideas include using different colours, textures, or more opacity on windows and glass walls. Shading, reflective solar blinds and curtains also alert birds to buildings.

Last fall, Toronto council created a set of Bird-Friendly Guidelines, a rating and certification system for measuring and registering bird-friendly buildings. The certification program, which isn’t yet mandatory, uses a colour-coded system to grade new highrise and office tower construction. As well as glass treatments, the new guidelines recommends the elimination of mirrored glass, searchlights, spotlights, rooftop and up-lighting, at least during migration periods.

For those folks who live or work in tall buildings, please do what you can to make your windows more visible to birds, and help our feathered friends live to fly again another day.

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Related links:
FLAP: Fatal Light Awareness Program
Form Follows Feathers: Bird-Friendly Architecture
Lights Out Toronto campaign
Toronto Star: “Must buildings kill birds?”
“Green building not so friendly to birds”



1. lavenderbay - April 8, 2008

A good survey on the different reasons buildings kill birds, and how the killings might be prevented.
I’d like to hear a little more on the experimental uv rays — I can’t see how they would help if they illuminated the potted palm in the window, for example. How do they work, at least in theory? I’m intrigued!

2. eyegillian - April 9, 2008

I’ve been looking for more information on ultraviolet glass coating, as well. So far I’ve found a report by Dr. Daniel Klem that appeared in the Bird Observer (vol 34, no 4, 2006). Here’s a quote:

“For some time now I have advocated the manufacture of a one-way type pane which, when viewed from the inside, appears the same as conventional glass, but from the outside shows visible patterns that birds will avoid.
Perhaps the optimal solution would be to apply patterns to glass that either reflects or absorbs ultraviolet (UV-A) wavelengths (ranging from 300-400 nanometers), a range of wavelengths that birds see but we do not. Of the relatively few but diverse bird species tested so far, it is hypothesized that just about all birds see UV light (perhaps nocturnal species are exceptions). The question of UV light serving as a signal to alert birds to the danger of glass is currently an active area of my research; however, as I write this, existing literature on the topic and my preliminary results are not encouraging (Graham 1997).”

If anyone else has insight on this or similar technology, I’d be interested in knowing more!

3. Catherine Bundy - January 7, 2009

Does anyone know of a way to make existing mirrored build “bird” friendly?

4. eyegillian - January 7, 2009

Good question, Catherine. The only thing I’ve seen is those hawk-shaped silhouettes attached to windows to warn birds away. Apparently you can also get patterned decals to attach to a window, and I’ve also read that blinds or patterned curtains are good for keeping birds away. I guess the main thing is to make the window as visible as possible, so anything — even posters or ads, like those see-through ones on buses — would help.

5. Cambren - May 13, 2009

On the top of this web page is small bird in a hand. Can you tell me what kind of bird that is.

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