Quote:
Originally Posted by IMBY
In a recent article in the New Republic magazine I was quite shocked by how many birds are killed every year with birds crashing into Glass buildings. The article concentrated on the new glass stadium in downtown Minneapolis which has killed 700 birds since it opened in the last year or 2. Which makes me wonder how many others are killed every years due to glass buildings.
Anyone know? And is there any alternatives?
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I work at a window manufacturer, and much of our business is in the NYC metro area. NYC recently passed "Local Law 15 of 2020", and I have been tasked with interpreting and coming up with materials and methods to comply with the law:
https://www1.nyc.gov/assets/building...b_2020-022.pdf
https://www1.nyc.gov/assets/building...e_document.pdf
How many birds are killed? According to the American Bird Conservancy, up to 1 billion birds are killed per year due to collisions with glass:
https://abcbirds.org/glass-collisions/
Most of these collisions occur at heights of 75 feet or lower. Birds mainly collide with glass not because it is see-through (though that is also a major factor), but because it reflects its surroundings around it. It reflects the sky, the trees, and other natural surroundings. The reason why NYC's law stipulates "75 feet or lower" for new glass installations is because that's the height of most trees. Birds often fly into glass because they see reflections of an adjacent tree branch or other resting place.
There are many ways to prevent bird collisions. Most of them involve putting a pattern on or over the glass to make them less reflective, less transparent, and more like an obstacle instead of a fly-through space. Solutions include:
- Insect screens, though these don't provide great indoor occupant views.
- Hanging cords spaced at 4" intervals over windows
- Glass frit patterns. These are "bird friendly" patterns made from ceramic printed directly on the exterior glass.
- Exterior or interior glass films with "bird friendly" patterns. Exterior films are far more effective because they reduce reflections.
- Glass etch patterns. These are "bird friendly" patterns etched on exterior glass using acid or sandblasting.
- Glass laminated patterns. These are "bird friendly" patterns on the inside film of laminated glass.
- Glass UV patterns. These are almost invisible to human eyes except at some angles or when wet. They take advantage of the fact that birds see at the UV spectrum, and can detect "bird friendly" UV patterns on the exterior glass.
By far the cheapest method to reduce bird strikes is either insect screens or hanging cords (only about $1-3 per SF). By far the most expensive method is the Glass UV patterns ($40-50+ per SF).