The 82-story Aqua Tower in Chicago appears to be waving with the wind. Its unusual, undulating facade has made it one of the most unique features of the Chicago skyline, standing out from the many rectangular glass towers surrounding it.
When designing it, architect Jeanne Gang thought not only about how people would see it, dancing against the sky, but also what it would look like to the birds flying by. The irregularity of the front of the building allows birds to see it more clearly and avoid fatal collisions. “It’s kind of designed to work for both people and birds,” she said.
As many as 1 billion birds die in building collisions in the US every year. And Chicago, located along the Mississippi Flyway, one of the four major north-south migration routes, is one of the riskiest places for birds. This year, at least a thousand birds died in one day after colliding with a single glass-covered building. In New York, which lies along the Atlantic Flyway, hundreds of species crisscross the skyline and tens of thousands die each year.
As awareness grows of the dangers posed by glittering towers and bright lights, architects are beginning to reimagine city skylines to design buildings that are both aesthetically bold and bird-safe.
Some are experimenting with new types of glass with patterns or coatings that birds can see. Others are completely rethinking glass towers and experimenting with exteriors that use wood, concrete or steel bars. Blurring the lines between inside and outside, some architects are creating green roofs and facades, inviting birds to nest in the building.
“Many people view bird-friendly design as just another building limitation, another requirement,” says Dan Piselli, director of sustainability at New York-based architecture firm FXCollaborative. “But there are so many buildings with progressive design that perfectly illustrate that this does not have to limit your design and your freedom.”
How modern buildings endanger birds
For Deborah Laurel, director of the Prendergast Laurel Architects firm, the realization came several decades ago. She was in the running for an award for her company’s renovation of the Staten Island Children’s Museum when the museum’s director told her that a number of birds had crashed into the new addition. “I was shocked,” she said.
She embarked on a frantic investigation to learn more about bird collisions. After several years of research, she discovered that there were few practical tips for architects, and worked with the conservation group NYC Audubon to develop a bird-safe building guide.
The problem, she discovered, was that the technological and architectural advances of the past half century had, in a sense, transformed New York City—and most other U.S. skylines and suburbs—into death traps for birds.
Before the 1960s, much of the large sheet glass used in buildings was made through a painstaking and expensive process of casting and polishing. The glass often contained bubbles or other imperfections that hindered its clarity.
Then, in the 1960s, float glass – made using a new technique that created uniform, clear plates – became widely available. “This new glass is very perfect: perfectly flat, perfectly smooth and it is also more reflective,” Laurel explains. In the decades that followed, builders also increasingly installed double glazing, which was intended to help insulate buildings and save energy, but had the added effect of making the glass even more reflective. “These two steps in technology have really impacted birds significantly.”
At certain times of the day, tall glass towers almost dissolve into the sky. At other times, the windows appear so bright that they are imperceptible to birds, which may try to fly through them. During the day, trees and greenery reflected on shiny building facades can deceive birds, while brightly lit buildings can confuse and bewilder them at night.
In an unfortunate turn for the birds, in the 1970s, the glossy glass look also became a popular design aesthetic, and the look has stuck around ever since. “It started with the good intention of wanting light-filled spaces, to give people a sense of openness,” Piselli said. “But the material has these multifaceted consequences.”
The changes that can save bird lives
About a decade ago, Piselli’s company was working on a half-billion-dollar renovation of New York’s Jacob K Javits Convention Center, a gleaming, glass-clad spaceframe structure that killed 4,000 to 5,000 birds a year. “The building was a black Death Star in the urban landscape,” Piselli said.
To make it more bird-friendly, FXCollaborative (then called FXFowle) reduced the amount of glass and replaced the rest with fried glass, which has a ceramic pattern baked into it. Small, textured dots on the glass are barely noticeable to humans, but birds can see them. The fried glass can also help reduce heat from the sun, keeping the building cooler and reducing air conditioning costs. “This has become kind of a model for bird-friendly design over the last decade,” Piselli said.
The renovation also included a green roof, audited by the NYC Audubon. The roof now serves as a refuge for various bird species, including a colony of herring gulls. Living roofs have since become popular in New York and other major cities, in a reversal of the decades-long practice of reinforcing buildings with anti-bird spikes. In the Netherlands, the facade of the World Wildlife Fund’s headquarters, a futuristic structure that resembles a billowing blob of mercury, contains nesting boxes and spaces where birds and bats can live.
The use of fried glass has also become more common as a way to conserve birds and energy.
Earlier this year, Azadeh Omidfar Sawyer, assistant professor of building technology at the Carnegie Mellon School of Architecture, developed open-source software to help designers create custom, bird-friendly glass patterns. A book of 50 patterns that Sawyer recently published features intricate geometric grids and abstract series of lines and blobs. “Any architect can pick up this book and choose a pattern they like, or they can customize it,” she said.
Builders have also experimented with UV-printed patterns, which are invisible to humans but observable to most birds. At night, conservationists and architects encourage buildings to turn off the lights, especially during migration season, when the bright glow of a city skyline can disorient birds.
And architects are increasingly integrating screens or grilles that provide both shade and visibility for birds. For example, the 52-story New York Times Building uses sintered glass coated with ceramic rods. The distance between the bars increases towards the top of the building, to give the impression that the building is dissolving into the air.
Gang’s work incorporates structures that can also serve as sunshades for birdwatchers, or as perches to observe nature. A theater she designed in Glencoe, Illinois, for example, is surrounded by a walkway made of a wooden lattice, giving visitors the feeling that they are in the canopy.
Gang rejects the idea of the iridescent all-plate glass building, “where you can’t tell the difference between the living environment and the sky,” and strives for the opposite. “I have always tried to make the buildings more visible with light, shadow and geometry, to create a more solid presence,” she said.
Gang has experimented with placing bird feeders around her own home in an effort to reduce collisions with windows, and she encourages other homeowners to do the same.
“I’ve noticed birds slow down and stop at feeders instead of trying to fly through the glass,” she said.
While high-rise buildings and large-scale urban projects receive the most attention, residential and low-rise buildings are responsible for the most bird deaths. “The big challenge is that glass is everywhere.” said Christine Sheppard, who directs the glass collision program at the American Bird Conservancy (ABC). “It’s hard to know what I know and not cringe when I look at it.”
Tips for improving your own home include using stained glass or patterned stickers that allow birds to see a window, she said. ABC has put together a list of window coverings and materials, ranked by how bird-safe they are.
Whether big or small, the challenge of designing buildings that are safe for birds can be “liberating,” says Gang, who has become an avid birdwatcher and now carries binoculars on her morning walks. “It gives you another dimension that you can imagine.”