Live in a house? Have a bird feeder? Ever heard a thud against a window, and wondered what made it? Chances are that it was a bird colliding with your window. The problem is that birds often don’t notice glass until they hit it. It could be that they simply do not see the glass, believing that they can keep flying to the object on the other side, or they may see reflections of the outside environment on the window, and believe they can fly to these reflections of objects. Such an impact would likely lead to brain haemorrhage, broken bones, or other internal injuries. Those that are not mortally injured often fall dazed to the ground where they face new threats. For an injured or stunned bird in winter, falling on frozen ground or snow would result in rapid loss of body temperature causing hypothermia and death. Then there are the predators that scavenge at the base of windows and buildings – Ring-billed Gulls, crows, raccoons, rats and cats are all opportunistic feeders that learn which buildings deal up the best menu.
In a published scientific paper, Environment Canada (EC) ranked window collisions as the second highest direct human cause of bird deaths in Canada, estimating that 16 million to 42 million (25 million midpoint) birds die from window collision annually in Canada. Ninety percent of these collisions are with windows in individual houses, about 9% from low-rise buildings, and <1% from high rises and skyscrapers. The problem only gets worse for the 8 of every 10 of our birds that leave our borders each fall. In the USA, there is much more glass and buildings. US estimates of window casualties of birds are placed at 100 million to a billion birds annually, based on the “1 to 10” birds per building/ house / year model often used. Many of these would be birds born in Canada, and either over-wintering or migrating through the USA.
For each category of building – from houses to high rises, the risk of collision increases with the amount of glass. Landscaping and other features around building also influence collision rates. Features that attract birds near glass like shrubs and trees raise the possibility of collision. Bird feeders between one and five metres of a window also increase the likelihood of collision. Feeders within a metre are much safer. Lights, including indoor lights radiating out of windows, also attract migrating birds (most species of songbird migrate at night), especially during weather conditions characterized by low clouds or fog.
FLAP Canada (Fatal Light Awareness Program) brought this issue to national and international prominence in the early 1990s, engaging volunteers in collecting shockingly high numbers of dead and injured birds from beneath Toronto’s skyscrapers. Initially the issue was portrayed as one of light attraction of nocturnal migrants, resulting in the collision of migrating birds against the windows of the tall buildings. FLAP developed a volunteer program in Toronto to salvage and rescue birds. Since its inception, FLAP has contributed to many other areas to address this issue, including policy development, collision prevention mitigation, education, research and rehabilitation. While the attraction of migrating birds to sources of artificial light and subsequent collisions is a serious issue in Toronto (leading to FLAP’s and the City of Toronto’s “Light’s out Toronto!” program) and many other cities and even from structures like offshore oil and gas platforms, it turns out to be less significant than daytime collisions with glass.
While many other individuals and groups have and are contributing to this issue, it is really through the work of Doctor Daniel Klem Jr. of Mulenburg College in Pennsylvania that the scope and magnitude of this issue was brought to light. Dr. Klem’s nearly 40 years of research and numerous published papers were key in helping us better understand the issue of bird collisions with windows and the effectiveness of markers for bird collision mitigation.
Legal responsibility: Provincial Court ruling places the law on the side of birds and conservationist
In 2012 and 2013 two landmark legal decisions, were made in the Provincial Court of Ontario, as a result of two separate lawsuits: Menkes v. Ontario Nature and Podolsky e v. Cadillac Fairview. Ecojustice Environmental Lawyer Albert Kohl, who argued the cases on behalf of FLAP and Ontario Nature, summed up a key court decision in this way:
“In Ontario the law is now clear: owners or operators of commercial buildings that reflect light that deludes birds into fatal or injurious collisions are in violation of the law. The federal Species at Risk Act is equally clear: the unintentional killing or injuring of listed (Threatened or Endangered) bird species in collisions with reflective windows of commercial buildings is an offence.”
FLAP Canada was called forth as a key witness for both cases. This decision, and the precedent that it set, is a landmark victory for birds, providing a strong incentive for building owners to practice due diligence when it comes to reducing risks to birds. It also provides an important legal tool to groups like FLAP to mobilize volunteers to monitor buildings, particularly those suspected of harming birds in this way.
There are few sources of easily available information on the species and numbers of birds that die from window collision. FLAP Canada has been one of the best sources from its Toronto program. FLAP published the results of collisions from between 1993 and 2010, totalling 52,006 individually of 165 species. Here is a list of ten highest ranked species with casualties between 1993 and 2010 with the total number in brackets:
- White-throated Sparrow (7879)
- Golden-crowned Kinglet (5802)
- Ovenbird (4057)
- Ruby-throated Hummingbird (2574)
- Dark-eyed Junco (2451)
- Ruby-crowned Kinglet (2369)
- Brown Creeper (2366)
- Hermit Thrush (1974)
- Common Yellow-throat (1952)
- Nashville Warbler (1680)
Thirteen species at risk were among the 165 species. Those with significant numbers include Wood Thrush (358), Canada Warbler (230), and Whippoorwill (70). All of these species are listed at Threatened on by COSEWIC, and Canada Warbler and Whippoorwill are both on Schedule One of the Federal Species at Risk list as Threatened.
In 2014, US scientists published a comprehensive analysis of all available data on bird collisions in the USA and Canada. Using the EC classification of buildings as houses, low to medium storey buildings, and tall buildings, the authors’ developed a vulnerability index of species, as it has become extremely apparent that there is a spectrum of vulnerability, beyond simple abundance. Not surprisingly, songbirds are the group of species most impacted, depending upon the type of structure.
Ten most vulnerable species by each category of buildings in the USA. Risk values indicate the factor by which species are at a greater risk of collision compared with a species with average risk.
|Houses||Risk value||Low rises (<12 storeys||Risk value||High rises (>12 storeys)||Risk value|
|Purple Finch||1066||Golden-winged Warbler||142||Townsend’s Solitaire||167|
|Ruby-thr. Hummingbird||175||Painted Bunting||129||Black-thr. Blue Warbler||78|
|Ovenbird||112||Ruby-thr. Hummingbird||104||Connecticut Warbler||52|
|Brown Creeper||81||Black-thr. Blue Warbler||86||Brown Creeper||44|
|House Finch||80||Swamp Sparrow||51||Ovenbird||44|
|Black and White Warbler||69||Canada Warbler||47||Ruby-thr. Hummingbird||43|
|Cedar Waxwing||51||Louisiana Waterthrush||46||Worm-eating Warbler||27|
|Field Sparrow||48||Brown Creeper||45||Canada Warbler||26|
|Wood Thrush||41||Yellow-bellied Sapsucker||38||Gray Catbird||24|
|Swainson’s Thrush||35||Connecticut Warbler||36||Yellow-bellied Sapsucker||24|
Fortunately as our understanding of these issues improves, so does our understanding of solutions. FLAP Canada has developed “BirdSafe”TM, a set of standards and an audit to assess buildings and their risk to birds. The American Bird Conservancy (ABC) has developed many resources; including a comprehensive guide to Bird Friendly Building Design. Many cities, including Toronto have created their own bird-friendly guidelines based on these standards. Below is a summary of mitigation measures for homeowners, and links to guidance for building owners and municipalities.
- Assess if there is a problem
Checklist of risk factors
- Large window – particularly the “bay window” types with continuous panes of glass
- Presence of trees, shrubs or flowers within 5 metres of the house
- Presence of a bird feeder between 1 and 5 metres from a window
- Within 100 metres of a forest, ravine or park with large amounts of natural vegetation.
- Evidence of dead birds in your yard or at the base of the window
If you have one or more of these risk factors, you should consider mitigation options below.
- Mitigation of window risk
You can protect birds from striking your windows by making the windows more visible to birds. This does not need to be at the expense of the view. Consider the options below and choose the right one for your tastes.
External blinds, solar shades, external screening or taut netting stretched across the window frame are all very effective means of making windows more visible to birds. Modern solar blinds are easy to install and can be mechanically controlled from inside the house. A temporary solution, if you have internal shades or blinds is to leave them partly open during the day.
Another way to make the windows visible to birds is by applying external tape. The “Feather friendly” products are promoted by FLAP. They result in lines of dots that create minimal visual disturbance. Patterns of tape (or dots) should result in no spaces more than 10 cm (4 inches) apart vertically or 5 cm (2 inches) horizontally. Alternatives to tape can be used, including tempura paint, patterned films and mobiles in front of the window.
Often in houses, one or two windows are responsible for the majority of collision deaths. Therefore mitigation can be focused on the problem windows rather than all windows in the house or building.
Help contribute to science on the impact of collision on birds by reporting all observation of birds that you believe are victims of a collision on the FLAP Mapper Web app. Otherwise, submit your bird observations in eBird.
We need testimonials!
You can also contribute directly to the understanding of this issue in the following way. If you have a window that you know is killing birds, and you have an idea of how many birds die from colliding with the window annually, we would like to know how your mitigation of the problem (through the application of tape, dots, netting, etc), has actually reduced the number of collisions. For more information on how to do this, contact Nature Canada at firstname.lastname@example.org and write “reducing window collisions” in the subject line.
What to do if you find an stunned or injured bird beneath your window
- Approach the bird and carefully place a towel or piece of cloth over it, then transfer it to a cardboard box (that air can get into) or a paper bag if necessary (with small holes to allow air in).
- Transfer the bird to a quiet and warm place
- Check on the bird every 30 minutes or so. If it is becoming more active (you hear it moving around), take the container and bird outside, set it on the ground and open it so the bird can see daylight. Step back and allow it time to fly away. If it doesn’t fly away, carefully close the container and take it back inside.
- If the bird does not recover within a few hours, take it to your nearest wildlife (or bird) rehabilitation centre.
Resources: (we will be adding resources to this page)
Builders, Architects and Municipalities – Building Design guidelines