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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

This white-throated sparrow was rescued by a WIngs volunteer, rehabilitated and released. © Scott Diehl
This white-throated sparrow was rescued by a WIngs volunteer, rehabilitated and released.

© Scott Diehl

April 2006

Threshold of pane

Collisions into windows pose the greatest manmade danger to songbird populations. We can take steps to significantly reduce those losses.

William Mueller and Scott Diehl

Attending to the injured
Clear solutions

It had been a rough winter for the wood thrush on her wintering grounds in Brazil. The lowland forest where she spent the last few winters had been cleared and was smoldering when she arrived last November.

She's had a difficult spring migration journey north to Wisconsin, too. When she arrived on the Texas coastline, thin and exhausted from crossing the Gulf of Mexico, the beachfront habitat she relied on for food, fresh water and rest was dotted with beachfront condos and radio towers. In Illinois, she narrowly escaped a hungry sharp-shinned hawk, also on its way north.

She was almost home. She had been flying at an altitude of over 1,000 feet for hours. As the first blush of dawn painted the eastern horizon, familiar shapes of the wooded hills and valleys of Wisconsin were revealed in the growing light. She began to descend, dropping down to face yet another grave danger. . .a landscape turned deadly, reflected in countless panels of plate glass.

Birds already run a gauntlet of dangers going about the daily business of searching for food, establishing and defending territories, nesting and raising young, or migrating to and from their wintering grounds. Adverse weather and predators are obvious threats in their natural surroundings, but additional manmade hazards unknowingly kill immense numbers of birds. At the top of this list? Collisions with glass windows.

Daniel Klem, professor at Muhlenberg College in Allentown, Pennsylvania, has studied bird/window collisions for years. Extrapolating his research results, Klem estimates that between 100 million and one billion birds of at least 225 species are killed by collisions with windows each year in North America alone. The numbers seem shocking for an event few of us see very often and rarely find first-hand evidence of. Birds killed following window collisions are quickly picked up by scavengers or may fall behind shrubs and other landscape plantings around homes or businesses where we don't notice them.

In the daytime, birds see the sky and landscape reflected in windows or they may see completely through a building where two windows line up. They do not realize that they cannot fly through these invisible obstructions. During spring and fall migration periods, the problem doesn't end when the sun goes down. Most of North America's songbirds migrate at night using the stars as navigational aids. These birds can be attracted to lighted buildings, especially tall ones, like moths to a flame, on their migratory path. Birds can collide with lighted window panes or, captivated by bright exterior lighting, will circle a building until exhaustion overtakes them. Confused and severely weakened, they drop to the streets and sidewalks below where they are at great risk of predation, accidents with vehicles, and collisions with reflections in low-level glass. Whether daytime or nighttime, one of every two bird collisions is fatal, and injured birds are often scavenged by gulls, crows, raccoons, cats or other predators.

Preventing such collisions is a focus for a small group of private organizations and governmental agencies. The Humane Society's Wisconsin Night Guardians for Songbirds (WIngs), aims to educate the public about this threat, find and rehabilitate injured birds, and work with building owners and tenants to reduce collisions with windows. WIngs is patterned after similar pioneering programs in Toronto (FLAP, Fatal Light Awareness Program) and Chicago (the Chicago Bird Collision Monitors).

Launched in the spring of 2005, WIngs staff works with owners, managers and tenants of Milwaukee's tallest buildings to make their buildings safer for migrating birds. Volunteers also search city streets in the pre-dawn hours for stunned, injured and dead birds. It takes a hardy, dedicated lot to patrol around tall downtown office buildings as early as 4:30 a.m. during spring migration to find birds before scavengers get them.

Live birds are gently captured and transported to the Wisconsin Humane Society's (WHS) Wildlife Rehabilitation Center at 45th and Wisconsin Avenues in Milwaukee. Dead birds are collected and transported either to the humane society or the Urban Ecology Center. Both centers are keeping records of the species found, specific locations and times each bird is found, and prevailing weather conditions. In compiling data, WIngs hopes to identify problem buildings and better recognize weather conditions that may increase the likelihood of window collisions. Collecting information in a consistent manner from WIngs, FLAP and the Chicago Bird Collision Monitors programs will make it easier to combine results into a single database to increase our collective knowledge about window collisions.

Attending to the injured

Injured birds arriving at the WHS Wildlife Rehabilitation Center are each placed in a warm, dark, quiet container and allowed to rest for 30 to 60 minutes. Handling birds too soon can lead to excessive stress that can kill them. Thereafter trained staff examine each bird, identify injuries, administer first aid and start treatment. Common injuries following window collisions include concussions and other head injuries, eye traumas, fractured bills and broken bones, especially the delicate bones in the bird's chest: the coracoids and furcula (the wishbone). These bones help support the bird's shoulder structure and when fractured, the bird cannot fly. The staff uses special splinting and stabilizing techniques to give the fractures a chance to heal.

Birds are initially housed in small, quiet habitats, with a minimum of exposure to humans so they can rest, eat and recuperate. An injured bird may stay in the rehab center a few days to several weeks, depending on its injuries. Once injuries are healed, each bird is evaluated for fitness. Some birds may need additional exercise in a large aviary, or even physical therapy before they are ready to go. When ready for release, southward migrating birds are transported south of the city, northbound birds are released north of town.

Clear solutions

Last year's International Migratory Bird Day (observed the second Saturday each May) featured the theme "Clear the Way for Birds!" and included handouts describing practical solutions for reducing bird collisions. The problem can only really be solved one window at a time. There are a variety of options: some simple and inexpensive, others more complex and costly, but all windows don't have to be treated the same.

On private homes and in low-rise apartment buildings, installing simple mesh or screen barriers on the outside of windows that have been a problem helps in two ways: screens cut down on reflections birds see in the windows, and they provide a relatively soft cushioning barrier between the bird and the window that helps prevent injuries. Many new window installations and retrofits come equipped with full length or full width fiberglass screens on the outside. If your home has older aluminum triple-track windows, the screens typically cover only half of the window, leaving one pane still uncovered. You can cover the wooden frame outside the edge of that pane with screening or finer-mesh plastic chicken wire that's available at most hardware stores. The mesh can be stapled in place outside the window if those windows can be opened from the inside for cleaning.

Roy and Charlotte Lukes of Baileys Harbor have gone a step further, installing mesh covering the large picture windows on their home. In addition, they fashioned strings with large turkey wing feathers and fastened them to the upper edge of some windows where they have observed bird collisions in the past. Any breeze sets these "feather-mobiles" in motion, hopefully letting nearby birds know not to venture too close.

Wild turkey wing feathers attached by strings to the window frames flutter in even light winds acting as scare devices. © Roy Lukes
Wild turkey wing feathers attached by strings to the window frames flutter in even light winds acting as scare devices.

© Roy Lukes

For a more finished look over larger, extensive sets of windows, one can purchase commercially-produced "bird screens" that are placed in frames over the windows. Such a set was installed at the Rowe Sanctuary, an environmental education building in Gibbon, Nebraska. These screens can be removed during seasons where fewer birds are present, but if bird feeders are stocked year-round, window treatments should be left up all year too.

Another way to largely eliminate reflections from the outside of windows is to apply specially-made films, such as a product called CollidEscape. These films adhere easily and last for years without obscuring the view from inside. The films can be pretty readily removed, even years later if necessary.

Professor Klem and his colleagues have also found that where bird feeders are placed affects the numbers and severity of window collisions. Feeders placed nearer than three feet from windows or farther away than 30 feet substantially reduce fatal bird collisions. The middle zone between those distances is much more dangerous for birds.

Other simple techniques can prevent or substantially lower the frequency of collisions. Moving house plants farther from windows can reduce visual confusion. Though houseplants need natural light, birds sometimes think they can perch on these plants, unaware that there is a pane of glass between them and the landing site. Stenciled designs or decals applied to the outside of windows can be nearly as useful as screens or other barriers, if they are of sufficient size and number. Falcon silhouettes placed widely apart are largely ineffective: silhouettes and other designs need to be placed no more than the width of a hand apart to provide an effective visual warning for small birds. At the Urban Ecology Center in Milwaukee, staff and volunteers have created a display of a variety of methods of treating windows to prevent or limit collisions. The Wings website has a gallery showing a variety of window treatments designed to reduce/prevent bird collisions.

You can also find directions for crafting temporary frosted pane window stencils at Fatal Light Awareness Program. Stencils are also available at home remodeling centers and craft shops.

Painting stenciled designs on windows helps warn birds away. © Jennifer Goyette
Painting stenciled designs on windows helps warn birds away.

© Jennifer Goyette

More extensive modifications may be more practical for new commercial construction rather than retrofits, including installing window glass at angles of 20 degrees or more, tilted outward at the top. Experiments show that angling glass downward is particularly effective at reducing collisions. Experiments with new types of window glass are also being conducted. Some new glass has a series of frosted "dots" on the outside that are barely visible inside yet eliminate reflections. Others are experimenting with ultraviolet coatings visible to birds but not to people. Perhaps "bird-friendly" glass will one day be standard for new construction and replacement windows.

A Birds & Buildings Forum held in Chicago last spring hosted a symposium on windows and building design. The forum, a small Chicago-based nonprofit group, encourages architects and design professionals to develop and build bird-safe windows and glass walls. The conference discussed window features that attract and kill birds. Although targeted for Illinois and Wisconsin architects, the event attracted attendees from as far as Atlanta, Seattle and Edmonton, Alberta. Sponsors included Chicago architecture schools, three architecture professional associations and the City of Chicago. The forum also provides information that can be incorporated in university courses so architecture students can learn about bird-safe designs as part of green architectural projects, said Randi Doeker of the forum.

Whether you are a homeowner, renter or small business operator, simple techniques offer economical options to retrofit windows or install simple screen barriers, window treatments, films and stenciling to reduce bird collisions. Placing bird feeders carefully and supporting community educational programs like the Wisconsin Humane Society's WIngs program, can also help us prevent injuries and save many more of the birds we cherish.

William Mueller chairs the Conservation Committee for the Wisconsin Society for Ornithology and the Issues Committee for the Wisconsin Bird Conservation Initiative. Scott Diehl manages the Wisconsin Humane Society's Wildlife Rehabilitation Center in Milwaukee.

Wisconsin Night Guardians for Songbirds
Bird screens and CollidEscape are available for purchase through the Wisconsin Humane Society.

Fatal Light Awareness Program

You can save birds from flying into windows!
A publication of the American Bird Conservancy

Clear the Way for Birds
The Danger of Plate Glass

U.S. Fish and Wildlife Service information about birds and collisions

Window Collisions
A publication of the Bird Conservation Network

Birds & Buildings Forum

Wisconsin Bird Conservation Initiative
Other collision resources

Chicago Bird Collision Monitors

Urban Ecology Center