For migrating birds, our cities are a deadly obstacle course.

Our cities today are annihilating birds by the millions. And it's a totally unintended consequence. No one said, let's figure out how to maximize how many birds we can kill by the way we're designing our buildings. But it's out of absolute ignorance that we're building buildings that are literally killing millions of birds every year.

--Carl Elefante, past president of the American Institute of Architects

Staggering losses, year after year
It is estimated that, in North America alone, about 1.3 billion birds die each year by colliding with buildings. To put this number in terms that may be easier to grasp, if each bird is one second, 1.3 billion birds is equivalent to 41 years and a couple months. Yet, even at such devastating numbers, window collisions are only the second most serious cause of mortality in birds. (The first is predation by outdoor-roaming domestic cats.) This rate of loss is simply unsustainable, and it is no wonder that, since 1970, the number of birds in North America has plummeted by a third -- and is still declining.
North America is the continent for which the most data has been collected, over the longest time. There is no reason to believe the numbers are any less severe on other continents, including Asia. The East Asian-Australasian Flyway, along which birds migrate from Alaska and Siberia through East and Southeast Asia to Australia and New Zealand, encompasses 37 countries and is home to some two billion people. Some of the most modern and densely populated cities -- Shanghai, Seoul, Hong Kong, Kuala Lumpur and Singapore, to name just a few -- lie within the flyway and constitute a high-risk obstacle course for birds that must traverse the region twice each year.

Why are our urban environments so dangerous for birds?

Artificial light For the many species of birds that migrate at night, our illuminated cityscape casts a glow into the sky that is disorienting and may act as an "ecological trap," luring migrants to stop over in urbanized areas, where their risk of colliding with buildings is increased. For this reason, some cities hold "lights out" campaigns during bird migration to reduce the amount of light pollution in the sky. After all, once office workers go home at the end of the work day, there's no particular reason for commercial towers to keep so many lights on. Turning even half of them off would help migrating birds and lower carbon emissions. We can all do our part by turning off unnecessary lighting and drawing the blinds at night. We might even get to see a few more stars at night.

Glass The transparent and reflective properties of glass are very useful to humans, but these same properties cause glass to be invisible to birds. Where windows reflect the surrounding landscape, birds perceive the reflected image as a continuation of their environment. In addition, the recent trend of installing transparent glass railings on walkways, staircases and balconies is especially deadly, particularly when potted plants are placed just behind the glass that may entice birds to fly towards them.

All Buildings Pose a Danger

It may seem that multistorey office towers are the biggest problem. Certainly, some mirrored-glass skyscrapers kill large numbers of birds. But studies estimate that tall buildings account for less than one percent of window fatalities. Taken together, low-rise buildings and residential homes, by virtue of their far greater number, cause the vast majority of bird collisions. We can all take action to make the buildings where we live and work safer for birds.

A word about glass railings

Glass railings have unfortunately become ubiquitous in newer homes. They are very dangerous to birds, especially when plants are placed enticingly behind them. Moreover, they add to the workload of cleaners and domestic helpers. Presumably they are popular because they are thought to offer homeowners an unimpeded view, but it must be said, people rarely sit on balconies or patios in the sweltering heat of the day!

Make your home a safe one for birds with these proven methods.