The birds are dying at alarming rates, chiefly because we have built them a city full of towering booby traps: Birds keep flying into the sides of glass-forward buildings, resulting in tens of thousands of avian deaths annually. As such, City Council Speaker Corey Johnson and Councilmember Rafael Espinal, Jr., have introduced legislation that would make our urban landscape less perilous for birds.

The New York City Audubon Society estimates that about 90,000 birds (maybe even as many as 230,000, according to a press release) get into fatal crashes with our local architecture each year because they can't see glass, just the scenes that glass reflects. (Which, in a skyscraper-heavy city, often means open sky.) Dark flight conditions tend to exacerbate the problem, according to NYC Audubon: "Especially in foggy or rainy weather when birds fly at lower altitudes, the combination of glass and light becomes deadly. Confused by artificial lights, blinded by weather, unable to see glass, or simply exhausted by flying around the lights like moths near a flame, birds can be injured or killed."

The bill, introduced on Thursday, would amend the building code to require that developers make 90 percent of glass used on new and altered buildings bird-friendly. According to Audubon, this would mean either using glass with a pattern on it, or adding a special coating—obvious to birds, more or less invisible to humans—to the windows. In a statement, Espinal said he saw no reason why city buildings "can't coexist with, and even enhance, the natural world."

"Avian creatures are a vital part of our ecosystem, and we neglect them at our own peril," he added. But also, there's the cost to consider: Audubon puts the price of bird-safe glass about 5 percent higher than regular glass, but a Newsweek investigation into the implications of bird-proofing NYC buildings estimated that it could be about 50 percent more expensive.

Pricing projections on this feature seem to vary widely: When considering construction plans for a new stadium for the Minnesota Vikings in 2015, for example, the Minnesota Sports Facilities Authority said the addition of bird-friendly glass to the design could cost about $60 million. (A NYC-based architect, meanwhile, estimated that the stadium design challenge could be solved for under $1.1 million.) Gothamist asked Espinal's office to ballpark the expected building costs, and a spokesperson deferred to the Architects Institute of America. We will update if we hear back.

On a national scale, U.S. Representative Mike Quigley introduced a bill in January, providing for bird-proofing on "each public building constructed, acquired, or of which more than 50 percent of the facade is substantially altered." Cory Booker reintroduced a similar bill in the Senate, around the same time. In NYC, some architects have already undertaken bird safety measures on their own. In 2015, for example, the Javits Center got a patterned glass makeover that not only slashed bird deaths by 90 percent, but also cut energy consumption by 26 percent: Fritted, i.e. printed, patterned, glass coats panels to reduce glare and cooling costs.

Which is to say, the high cost of construction could be offset somewhat by savings—both in terms energy and avian lives snuffed out by bamboozling glass.