Bird-Friendly Building Manager - Bird Migration Advisory (2012)
An Animal Rights Article from All-Creatures.org

FROM

Fatal Light Awareness Program (FLAP)
August 2012

An estimated 1 to 10 birds die per building, per year. The City of Toronto has over 950,000 registered buildings that could potentially kill over 9 million birds each year. Across North America, the estimated number of migrating birds killed annually in collisions with buildings ranges from 100 million to 1 billion birds.

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An estimated 1 to 10 birds die per building, per year. The City of Toronto has over 950,000 registered buildings that could potentially kill over 9 million birds each year. Across North America, the estimated number of migrating birds killed annually in collisions with buildings ranges from 100 million to 1 billion birds.

Windows are everywhere: in our homes, offices, stores, restaurants, vehicles, bus shelters...everywhere. Many ornithologists now claim that collisions with human-built structures are the leading cause of migratory bird mortality in North America.

North America sits beneath four of the world’s busiest migratory bird corridors: the Pacific, Central, Mississippi and Atlantic Flyways. The Central Flyway sends birds across and around the Great Lakes. This natural passage offers visual cues for birds to follow and provides major stopover areas where birds rest and feed throughout their journey.

Tragically, coastlines that were once unobstructed to migration are now obstructed by the tall, lighted office towers and reflective buildings of our urban areas—a deadly obstacle course for migrating birds.

Frequently Asked Questions:

Why do birds collide with windows during the day?

Migratory birds live in forests, meadows or wetlands, and do not understand the concept of glass. To a migratory bird, glass is an invisible and dangerous obstacle. They see the landscape reflected in windows and mirrored building exteriors and mistake the reflection for shelter. Or birds see beyond the glass to interior potted plants or trees inside the building. Where windows meet at the corners, or line up with each other front and back (i.e., glass walkways, solariums, greenhouses) birds perceive clear passage and try to fly through to the trees they see on the other side.

Any reflective or transparent surface used in construction—from windows in modest city homes, to bus shelters, to mirrored exteriors on high-rise buildings—can be the site of fatal bird collisions. Daytime collisions often occur the morning after a bird has been drawn to buildings by excessive night-time lights. They get trapped by the maze of building reflections in this cycle of confusion and unnecessary death.

Why do birds collide with buildings at night?

Most species of songbirds migrate at night. They rely, in part, on the moon and the constellations to guide them along their migration route. The overnight lighting used in dense urban areas confuses migratory birds, and especially on foggy or rainy nights when cloud cover is low. Under these conditions, birds migrate at lower altitudes and are drawn to lights shining from office towers and other structures. Where spotlights are used to illuminate a building, birds fly “into” the beams of light and are reluctant to fly back out into the darkness. Often, they collide with the buildings or drop to the ground from exhaustion.

When day breaks, birds that managed to survive the night-time lighting hazards find themselves trapped in a maze of tall buildings with reflective surfaces. It is extremely difficult for migratory birds to escape this maze without striking windows and building exteriors, often with fatal results.

How many birds die in collisions with buildings each year?

An estimated 1 to 10 birds die per building, per year. The City of Toronto has over 950,000 registered buildings that could potentially kill over 9 million birds each year. Across North America, the estimated number of migrating birds killed annually in collisions with buildings ranges from 100 million to 1 billion birds.

What other kinds of human-built structures are responsible for bird deaths?

Any human-built structure that incorporates glass or reflective building material into the design can be the site of bird collisions during the day. This includes bus shelters, car windows, houses, greenhouses, solariums, office towers, restaurants, and any other structures where windows and/or reflective surfaces are present. At night, transmission towers, office towers, monuments, lighthouses, oil rigs-virtually any tall illuminated structure can be responsible for bird deaths. Collisions with buildings are a leading cause of migratory bird death, second only to habitat loss.

What is the impact of wind turbines on migratory birds?

The number of bird fatalities due to collisions with wind turbines sits well below the number of bird fatalities from collisions with buildings; however, birds are killed by wind turbines.

The National Wind Coordinating Collaborative fact sheet recognizes two types of impact on birds at wind facilities: direct mortality from collisions, and indirect impact from habitat disruption, habitat avoidance, habitat abandonment and the changes in instinctive bird behaviours due to the presence of wind turbines. Most of the bird fatalities are songbirds, but raptors are also killed when wind turbines are erected in open areas where these birds hunt for prey.

We believe in the development of renewable energy sources, but we are highly concerned about the bird fatalities documented at the locations of wind turbines. We encourage a thorough, independent, environmental assessment of proposed wind turbine sites. We encourage that those proposed sites be well away from migratory bird routes and rest areas. We encourage wind turbine developers to take full responsibility to protect migratory birds and other wildlife from injury and death.

When do birds migrate?

Birds migrate in the spring to their summer nesting grounds in northern Canada. In the fall, they fly south, back to their winter feeding areas. Depending on the species, winter feeding areas might be anywhere from southern Canada to the southern tip of South America.

Migration is triggered by an increase (in the spring) or a decrease (in the fall) in the phototropic period: the number of hours of daylight. The onset of both spring and fall migration fluctuates mildly, but generally spring migration begins in mid-March and continues until the beginning of June. Fall migration begins in early August and continues until mid-November.

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