Whitepaper: Bird--Glass Collision Mitigation for Invisible
Barn
Introduction: Collisions with human-built structures are a leading
cause of migratory bird mortality in North America, second only to
habitat loss1 2.
Birds cannot see glass. They see a reflection of their habitat (trees,
bushes, water, sky) in windows or in the mirrored exteriors of office
towers and other structures. Deceived by the reflection, birds often
collide head-on with the windows and buildings. From a bird’s
perspective, glass is an invisible barrier to their habitat.
Many migratory birds die on impact, or sustain serious injuries that
prevent them from continuing their journey. Stunned birds fall to the
ground and become vulnerable to predation.
Resolution: there are many common myths about bird deterrence. Hawk
silhouettes, single window decals, noise, plastic owls, and magnetic
fields are popular but ineffective.
To actually prevent bird collisions, deceptive glass and building
reflections must be visually disrupted.3 Decals, netting, screens,
paint, feathers, beads and other objects have been used successfully to
create bird-glass awareness when used correctly.4
The organization that spearheads bird deterrent initiatives in Canada,
the Fatal Light Awareness Program (FLAP.org), recommends uniformly
covering windows with a pattern of any shape so that the pattern
elements are separated by 10cm (4 in) if applied in vertical columns or
by 5 cm (2 in) if applied in horizontal rows. Window screen, ribbons,
decals, string, whitewash and other materials can be used with good
results.5
1
http://mag.audubon.org/articles/birds/when-birds-and-glass-collide
2
http://www.muhlenberg.edu/main/academics/biology/faculty/klem/aco/Birdwindow.html
3
Klem D. 1990. Collisions between birds and windows – mortality and
prevention. Journal of Field Ornithology 61(1):120-128.
4
http://www.birdwatchingdaily.com/featured-stories/15-products-thatprevent-windows-strikes/
5
http://flap.org/residential.php
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Unfortunately, effective patterning can create an undesirable
appearance, or difficult viewing for humans.
Some retrofit products can help mitigate this problem. For example,
fritted glass (glass with ceramic dots or patterns baked on) is visible
to birds, while significantly reducing solar gain and saving lots of
energy6.
And window film is transparent marking that is applied to the exterior
surface of glass at a specific spacing and contrast to provide
visibility to birds. Feather Friendly Technologies7, CollidEscape8 and
custom artistic window films are available.
While window films and fritted glass are designed to deter birds while
providing an attractive appearance to people, they may still be visible
and may detract from architectural design.
A better solution is suggested by the different biology of avian and
human vision: birds can see ultraviolet (UV) light, while humans
cannot. Research indicates that birds are alerted to the presence of
glass when they detect a UV pattern applied to a window.9 UV patterns
are essentially invisible to humans.
UV strategies for bird-glass collision deterrence include:
1. ORNILUX Bird Protection Glass has a patterned, UV reflective
coating, making it visible to birds while remaining virtually
transparent to the human eye.10
http://www.treehugger.com/sustainable-product-design/are-leedcertified-buildings-bird-killing-machines-in-a-word-no.html
7
http://www.featherfriendly.org/
8
http://www.collidescape.org/
9
2013. Evaluating the Effectiveness of Select Visual Signals to Prevent
Bird-window Collisions. Klem Jr., D and P. G. Saenger. 2013. The Wilson
Journal of Ornithology 125(2):406-411.
10
http://www.ornilux.com/
6
2. WindowAlert window decals and UV liquid reflect UV light to alert
birds to glass.11 However, the decals are visible and must be
placed densely to be effective.
3. David Sibley, the Godfather of American birding, reports good
results from using fluorescent highlighting pens to mark window
glass. The only problem seems to be the need to reapply regularly
to counter fading.12 Permanent UV inks may be more durable, and
there are invisible formulations.13 14 Invisible ink-jet printer
ink might be applied by dusting.15
Regular application of UV ink seems to offer the simplest, least
aesthetically disrupting, and least expensive solution to bird-glass
collisions, especially in a temporary installation.
http://www.windowalert.com/
http://www.sibleyguides.com/2007/11/a-potential-simple-method-forbird-proofing-windows/
13
http://www.globright.com/invisibleinkpen.html#anchor_484
14
http://www.maxmax.com/aUVBlueInvisibleInks.htm
15
http://www.ebay.com/itm/Invisible-Ink-UV-Ink-for-inkjet-printers-6UV-colors-/120738200403
11
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