A Window into Declining Bird Populations

The National Audubon Society recently released a comprehensive Climate Report summarizing 30 years of data including citizen-scientist observations from the North American Breeding Bird Survey, the Audubon Christmas Bird Count, and eBird. Included in the list are 314 bird species (more than half of all 588 North American bird species!) predicted to go extinct by the end of the century if we don’t prioritize conservation in future industry regulations and land/water management decisions.

Sadly, over 25% of United States bird species have declined to such an extent they are officially listed as being of conservation concern. In addition to habitat loss and predation by outdoor cats, one of the primary causes of bird deaths is one that many people would never think of - window collisions. Birds don’t recognize transparent glass as a solid object so instead of avoiding it, they attempt to fly directly towards reflected habitat, or through the invisible surface. Although accurate quantification is difficult, it’s estimated that 300 million to 1 billion birds are killed annually by window collisions in North America alone. 

For many reasons migratory birds are especially vulnerable to anthropogenic forces. In particular, they depend on multiple habitats including their breeding and overwintering habitats and that which lies along their entire migration route.  Habitat loss is considered the primary cause of bird population declines, but one could easily make the case that building large glass structures in the middle of a migration path would also qualify as habitat loss. It’s estimated that 5% (1 in 20!) of fall migratory birds meet their deaths by colliding into one of our windows. This is a tragically large number. The thing about migratory birds is that many of them travel by night or at high elevations so we don’t even see them. Here is an example of a NEXRAD imaging photo capturing bird migration.

 
In addition to the increase in densities, migratory birds navigate towards light and are thus attracted to our lit windows. This is why programs such as “Lights Out” have been so effective.  FLAP (Fatal Light Awareness Program),  Chicago Bird Collisions Monitor, and other Audubon Lights Out programs in North America.

THE PROBLEMS
The primary factors leading to high numbers of bird-window collisions (BWC) are:

• Tunneling: the effect created by glass-faced buildings coupled with interiorly lit objects (Klem et al., 2009 and Martin, 2011).
• Transparency: birds cannot detect the presence of glass and attempt to fly through (Johnson and Hudson, 1976).
• Reflectivity: glass reflects habitat and open space causing collisions (Banks, 1976)
• Adjacent habitat: attracts birds and is reflected in buildings (Gelb and Delacretaz, 2006).
• Migration: increases the number of birds which pass through an area exponentially, particularly birds that are not adapted for urban buildings (Codoner, 1995 and Collins et al., 2008).

THE SOLUTIONS
Based on count data, it’s actually thought that majority of total bird window collisions occur at people’s homes. You might not think that bird-safing your windows at home or at your work-place will make much of a difference, but you very well could save dozens of birds by doing so. There are a number of different things you can do to your windows to prevent bird strikes.

In addition, these are 3 simple practices that will reduce risks at home:

• Move feeders close to your windows — 1.5 feet or closer. From this distance, birds won’t be able to build up enough momentum to hurt themselves if they do fly against the glass.
• Close curtain and blinds when possible to break up the illusion of clear passage or reflected habitat.
• Move houseplants away from windows. Birds may view them as refuges and try to perch on them.

Here is a recent National Geographic article “How Better Glass can Save Hundreds of Millions of Birds per Year,” which discusses some of the past and current research being done.

THE CASE OF THE MINNEAPOLIS VIKINGS STADIUM

If you are like me one year ago, you are not aware of the severity of the bird-window collisions problem. I became deeply involved with this issue when I started volunteering as the Conservation Chair for the Audubon Chapter of Minneapolis and learned about the plans for the new Vikings stadium located in the center of the Mississippi River Flyway (the largest migratory flyway in North America, through which approximately 50% of all N. American birds pass).

This stadium is a $1.024 billion dollar project, nearly half of which is public money. Allocation of this large pool of resources towards the stadium was an issue of controversy to begin with, but public discontent skyrocketed when the Minnesota Sports Facilities Authority (MSFA) settled on a design featuring 200,000 sq. ft. of highly reflective glass in the middle of the country's largest migratory flyway – placing them in violation of several Minnesota laws including the Migratory Bird Treaty Act, the Minnesota Sustainable Building Guidelines, the Endangered Species Act, and the Minnesota Environmental Rights Act.

For less than 0.1% of the cost of the stadium, the MSFA could have opted for "fritted glass", used in the Dallas Cowboys stadium and the Javits Center in NYC.  It’s barely visible to the human eye, particularly at a distance, but the benefits are huge.

This type of glass was originally designed for energy conservation, but has the added benefit of reducing transparency and reflection just enough that birds can see it and avoid deadly collisions. This would have created a win-win-win situation in which there are countless fewer bird deaths, an unobstructed view for stadium-goers, and fewer Minneapolis taxpayer dollars spent on heating and cooling the building. However, despite nearly 100,000 public signatures, unanimous resolutions by the Minneapolis and St. Paul City Councils, the efforts of many expert scientists and conservationists requesting the use of bird safe and energy efficient glass in the stadium, the MSFA and Governor Dayton have refused to budge on this issue. Although the Michele Kelm-Helgen at the MSFA has come out with a series of contradictory and easily refutable arguments, it’s clear that the decision to use the reflective glass is only a matter of aesthetic preference.

We no longer live in a time when aesthetic preference is justification for the deaths of many thousands of protected animals. As society continues to grow and develop, there are many arising challenges for which this choice is not so clear. For example, the development of wind and solar power has many environmental benefits, but also contributes to the deaths of migratory birds. These choices are more difficult for whatever the choice, there is a high cost. For the Vikings stadium, and other buildings like it, this tradeoff does not exist. When the money is available (or the ROI is high, as is often the case), the ONLY acceptable option is to create structures to be as environmentally friendly as possible.

For more on the stadium and links to articles on bird window collisions, visit the Facebook page: https://www.facebook.com/birdsafestadium

Watch this informative video produced by Jim Gambone:
https://www.youtube.com/watch?v=ngvN7oHhHwY

Listen to this radio interview with activist Jim Gambone:
http://www.kfai.org/northern-sun-news/playlists/20141023

For more on Bird Conservation in the United States, check out this comprehensive yet concise report, "The State of the Birds".

References:

Banks, R. C. 1976. Reflective plate glass - a hazard to migrating birds. BioScience 26(6):414.

Codoner, N. A. 1995. Mortality of Connecticut birds on roads and at buildings. Connecticut Warbler 15(3):89-98.

Collins, K. A. and D. J. Horn. 2008. published abstract. Bird-window collisions and factors influencing their frequency at Millikin University in Decatur, Illinois. Bird-window collisions and factors influencing their frequency at Millikin University in Decatur, Illinois 101(supplement):50.

Evans-Ogden, L.J., 2002. Summary Report on the Bird Friendly Building Program: Effect of Light Reduction on Collision of Migratory Birds. Special Report for the Fatal Light Awareness Program (FLAP) (available from FLAP). 29 pages.

Hager, Stephen B., Bradley J. Cosentino and Kelly J. McKay, 2012. Scavenging effects persistence of avian carcasses resulting from window collisions in an urban landscape. J. Field Ornithol. 83(2) 203-211.

Harden, J. 2002. An overview of anthropogenic causes of avian mortality. Journal of Wildlife Rehabilitation 25(1):4-11.

Johnson, R. E. and G. E. Hudson. 1976. Bird mortality at a glassed-in walkway in Washington State. Western Birds 7:99-107.

Klem, D., Jr. 1989. Bird-window collisions. Wilson Bulletin 101(4):606-620.

Klem, D. Jr., D. C. Keck, K. L. Marty, A. J. Miller Ball, E. E. Niciu, C. T. Platt. 2004. Effects of window angling, feeder placement, and scavengers on avian mortality at plate glass. Wilson Bulletin 116(1):69-73.

Klem, D. Jr., C. J. Farmer, N. Delacretaz, Y. Gelb and P.G. Saenger, 2009. Architectural and Landscape Risk Factors Associated with Bird-Glass Collisions in an Urban Environment. Wilson Journal of Ornithology 121(1): 126-134.

Klem, D. Jr. 2009. Preventing Bird-Window Collisions. The Wilson Journal of Ornithology 121(2):314–321.

Ley, H.W. 2006. Experimental examination of the perceptibility of patented bird- protecting glass to a sample of Central European perching birds. Max Planck Institute for Ornithology, unpublished report [English translation available from ABC].

Loss, Scott R., Tom Will, Sara S. Loss and Peter P. Marra, 2014. Bird–building collisions in the United States: Estimates of annual mortality and species vulnerability. Condor 116:8-23. DOI: 10.1650/CONDOR-13- 090.1

Martin, G.R. 2011. Understanding bird collisions with man-made objects: a sensory ecology approach. Ibis 153:239-54.

Sloan, Allison, 2007. Migratory bird mortality at the World Trade Center and World Financial Center, 1997-2001: A deadly mix of lights and glass. Transactions of the Linnaean Society of NY 10:183-204.