Once, the most challenging obstacle flying birds faced was taller trees. However, with the advent of the skyscraper and other towering structures, our feathered friends have had to learn how to avoid crashing into them.
Builders can play a prominent role in protecting birds from injuries — and worse — by designing structures that reduce the risk of accidental collisions. In many cases, incorporating these strategies into a building's design is a legal requirement. The Bird-Safe Buildings Act stipulates that all buildings constructed, acquired or substantially altered by the General Services Administration must comply with various standards developed by the American Bird Conservancy (ABC). Many state and local jurisdictions have enacted similar bird-safe building guidelines.
The Leadership in Energy and Environmental Design (LEED) rating system determines whether a building provides sufficient protection for flying birds. A structure can attain an acceptable status by earning points to meet the designated threshold.
To determine the threat level, a series of birds engage in a test where they fly through a tunnel-like structure toward two windows — one consists of clear glass, and the other features the pattern undergoing testing. A net stops the bird before it reaches the ending point. If the bird approaches the patterned glass and then changes course toward the transparent panel, it indicates that it sees the pattern and knows to avoid it.
Tabulating the threat factor score entails dividing the total number of tested birds by how many flew toward the patterned glass pane. If too many birds fly directly toward the patterned pane, the material does not adhere to the standard.
Other assessment parameters include the absence of see-through passageways that could increase the collision risk. There should also be shielding of exterior lighting to avoid attracting birds after dark.
Building designers can implement several steps to improve bird safety.
We've all heard sad stories about birds flying into clear glass windows. Treating the glass to make it more opaque can alleviate this problem by helping birds notice the surface ahead of them. Frosting or etching can allow natural light to infiltrate the building without causing reflectivity that hinders the birds' visibility. Installing stained or ultraviolet-patterned glass is also an effective solution.
Fritted glass utilizes ceramic dots to reduce light transmission while alerting birds that they're approaching a window. Arranging these "frits" in specific patterns delivers the best results for preventing window collisions.
Screens that cover higher windows can keep birds from crashing into the glass. While screens may not totally obscure the glass, they can produce a tunnel effect that forms a protective barrier. Netting works similarly to screens but provides more flexibility. Placing the nets far enough from the windowpanes is essential to keep birds from colliding with them.
Placing tape or stickers on the interior of a window at specific intervals offers a practical and cost-effective solution for deterring bird collisions. Several bird-repellant tape products are available, although highly visible decals can typically deliver reliable results.
Artificially generated light can often distract and confuse birds, potentially leading to collisions. Placing opaque shields around fixtures keeps the light from projecting upward to the sky, eliminating the hazard. It can also prevent disruptions to the birds' routes during the migration season.
Bright lights can attract flying birds, especially at night. Turning off interior lights when not in use can minimize the risk. Another option is to install motion sensors that keep unused lights from operating continuously. An added benefit is that building owners can reduce energy and electricity consumption and lower their utility costs.
Many building owners in urban areas plant greenery on their roofs to create natural bird habitats. They can use these rooftop gardens to build nests for their young ones and seek refuge from predators. These structures also establish ecosystems that enable bird populations to thrive.
An important consideration when designing a green roof is the structure's proximity to glass, including in neighboring buildings. Implementing many of the preceding steps on upper windows may be necessary to minimize the collision risk.
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