Authored by Dr. Daniel Klem Jr., Sarkis Acopian Professor of Ornithology and Conservation Biology at Muhlenberg College, PA.

Renowned ornithologist Dr. Daniel Klem returns to the Walker blog to continue his series, “Bird Safe Glass Explained”. Dr. Klem gives insights into the results that building owners can look forward to when they build with bird friendly glass. In this article, he examines the performance of AviProtek® bird friendly glass at Swarthmore College, PA.

Bird friendly glass at Swarthmore

Swarthmore College is a prestigious institution of higher education in the greater Philadelphia, Pennsylvania (USA) area. It maintains a distinguished commitment to building that meets the highest environmental standards. The campus is an arboretum, lush with attractive vegetation that is individually labeled and tastefully placed among classroom, administrative, and residence buildings. The college grounds are an oasis of forested habitat cultivated within a suburban setting, surrounded by an urban landscape. In 2017 and 2018 the college installed AviProtek® bird friendly glass from Walker in two of its new buildings, making bird deterrent glazing a component of its sustainably building strategy.

Swarthmore has a Green Team dedicated to ensuring environmentally sound practices across campus life, from daily menus to major construction projects. The Green Team works with each building project’s overseers and architectural team to develop structures that blend into the surrounding environment and cause no harm to the natural world. Another attractive feature about Swarthmore is their Quaker heritage, which guides the institution toward consensus-driven decision-making processes.

The campus community overall takes part in policies and commitments. Early in the 2000s, starting with their glass-covered science building, Swarthmore used dot-patterned windows that my scientific studies had proven to be effective in preventing fatal bird strikes. Thereafter, the college eagerly selected Walker’s bird friendly glass for use in several high-profile campus buildings.

Bird friendly glass at Swarthmore

Developing effective bird-deterrent glass

Repeatedly validated peer-reviewed science has developed trustworthy guidelines on how to deter bird-window collisions. Walker read, analyzed and participated in these studies, then applied the learnings toward developing their bird friendly AviProtek® glass products. As part of the first comprehensive research about birds and windows, my experimental studies revealed that in order to effectively deter bird strikes, elements of any shape making up a pattern must be separated by no more than 2 inches (5 cm) if oriented in horizontal rows and by 4 inches (10 cm) if oriented in vertical columns. Furthermore, the pattern elements must be distributed across the entire surface of a pane of glass. This spacing of pattern elements is known as the 2 x 4 Rule. If vertical spacing is reduced to 2 inches, the resulting guideline is designated the 2 x 2 Rule.

Another significant and proven finding is that that pattern elements need to be placed on the 1st surface, the outermost surface in a window unit. During the daytime, most windows cover interiors which are darker than the outside world. When seen from outside, even a perfectly clear pane will act like a mirror when covering a dark interior space. Pattern elements on surface 1 solve this problem because the pattern markers interrupt reflections and alert birds to the presence of an obstacle.

Extensive evidence reveals that clear and reflective glass is invisible to birds. Collisions often occur when birds try to reach habitat and sky seen through clear glass or reflected off mirrored panes. My early studies, validated by many others, inform us that if the 2 x 4 Rule is applied to surface 1 it will reduce the risk of a bird strike by 93-94%. The effect is even greater when patterns follow the 2 x 2 Rule, eliminating bird kills entirely at most installation sites.

Results with AviProtek® bird friendly glass

AviProtek® E bird friendly glass with low-e coating on surface 2 has been installed in Swarthmore’s newest campus buildings. PPR Apartments opened for residential use in the fall of 2017, while Whittier Building opened its doors in the fall of 2018. Each of these structures incorporates acid-etched AviProtek® E glass pattern 213, a horizontal stripe with lines spaced 2 inches apart. This pattern meets the requirements of the 2 x 2 Rule and 2 x 4 Rule.

Campus records document only one bird strike at each site over the past four years at PPR Apartments and over the past three years at the Whittier Building. By comparison, over the last four years, 12 bird strikes were recorded at the  conventional windows of the Kohlberg campus building. This is especially significant because the Kolhberg building has a noticeably lower window to wall ratio than Whittier Hall and the PPR Apartments. 

Dr. Carr Everbach, a long-standing member of the Swarthmore College Green Team, offers the following testimonial statement:

“The patterned Walker glass on the PPR Apartments and Whittier buildings at Swarthmore is far more effective at preventing bird strikes than other glass patterns on campus. Over several years, there has been fewer than one documented bird collision each year on the patterned glass.”

Professor E. Carr Everbach, Chair, Swarthmore College Environmental Studies

Why the results matter

Birds the world over have significant economic and spiritual value for humans. A 2019 scientific study documented a loss of 3 billion (29%) from the entire bird population of North America since 1970. Bird-window collisions are a principal cause of this decline. Furthermore, the science informs us that collision with glass claims the fittest members of a species as well as less fit individuals. In other words, windows are indiscriminate killers. They do not “weed out” lesser individuals from the gene pool. Instead, they kill the strongest as well as the weak.

As the most powerful and dominating life form on Earth, we have the responsibility to protect the species which share our planet. Our world depends on healthy biodiversity to ensure sustained health for ourselves and those generations to follow. Current and continuing scientific research confirms that birds are killed hitting windows wherever glass and birds coexist, so it is critical that we use bird friendly glass in construction to protect and preserve our birds from built environments worldwide. Walker Glass has been a guiding leader developing and making bird friendly glass available for commercial sale and use. We see the results of these efforts in places like Swarthmore College, where bird friendly glass has reduced bird mortality wherever it is installed.

At Swarthmore, staff have been able to reduce birds strikes dramatically at the PPR Apartments and Whittier Hall by installing AviProtek® bird deterrent glass. Imagine what a difference it would make if all university and college campuses adopted this kind of approach! Fortunately, more and more schools, businesses and other institutions are joining the movement toward ecologically sound development. With municipal legislators on board, the movement is gathering steam among forward-thinking developers. Will you and your clients be among them?

About Dr. Daniel Klem Jr.

Daniel Klem Jr. is a United States ornithologist, known for his pioneering research into the mortality of birds due to glass windows. He is currently a Sarkis Acopian Professor of Ornithology and Conservation Biology at Muhlenberg College.

His research has influenced the design of buildings, not least the Niagara Falls State Park Observation Tower, on which he was a design consultant. He holds several US patents relating to windows design. He has also written about the birds of Armenia.

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