Bird-Window Collisions: How Big A Deal Are They?
Carol Quantock
November 9, 2025
Carol Quantock, a CDHS stalwart (she does our newsletters) spoke about Bird-Window Collisions: How Big a Deal Are They? (And what can be done to reduce them?)
For those who may not recall Carol’s previous presentation, a bird is a warm-blooded creature (though descended from dinosaurs), with feathers and wings enabling them to fly (which humans cannot, without technology). Birds are good. Windows are those transparent rectangles on the outer walls of homes, also good. But when birds and windows collide, it’s not good.
Carol said her talk was aimed at residential home-owners. She showed a slide depicting a typical backyard, a common bird habitat. Noting that only in the last 200 years or so has window glass become clear enough to endanger birds. Carol stated that with suburban sprawl, “it’s impossible to calculate how much glass is out there.” It’s not that birds try to fly through it into homes; rather, the glass reflects an outdoor scene. And birds don’t understand the concept of reflective glass windows.
She cited the work of Dr. Daniel Klem, Jr., who has studied this problem for nearly half a century. Windows are our biggest bird killers — they kill more birds than cats. Actually, windows kill practically no cats. But they kill almost twice as many birds as cats do. Around a billion annually, in the U.S. alone.
As for remedies, one obvious answer is education. However, Carol did not address this. Probably because it’s very hard to educate birds on the dangers of window glass.
The chief alternative is to reduce the degree to which windows reflect an outdoor vista which birds will think they can fly through. Carol stressed the “2×4” rule — breaking up the seeming window image into 2 by 4 inch rectangles, through which only very small birds could fit. This can be achieved mostly with stickers and decals; she mentioned a commercial product, “ColidEscape,” which can be plastered onto the outside of a window, making a nice image that’s actually transparent when seen from inside. “Bird tape” and “Feather Friendly” are cheaper options. Another remedy is window blinds. There are also modern window glass products that reduce reflectivity. A further piece of advice was to place bird feeders close to windows.
Carol finally spoke about why birds matter, calling them part of the “great circle of life,” providing us with enjoyment. She did not mention Mao Zedong’s 1950s campaign to exterminate swallows; billions were killed; turned out those birds ate a lot of insects, whose populations then exploded, with dire results for Chinese agriculture, and numerous human starvation deaths.
Recap prepared by Frank S. Robinson
