EVANSTON, Ill. (CBS) — Chicago ranks among the deadliest places for birds.

Thousands crash into the city’s buildings every year, and the problem also affects the Evanston campus of Northwestern University – where nearly all-window buildings have caused hundreds of bird deaths.

Since birds finish flying south this month, the CBS 2 Morning Insiders visited campus to see how they kept our feathered friends safe.

“Chicago gets millions of birds that pass through here every year,” said Annette Prince, the director of the Chicago Bird Collision Monitors.

Prince also said many of the birds’ journeys end after they crash into windows.

“We find 5,000 a year downtown in Chicago,” she told CBS 2’s Ryan Baker.

It is a concerning number, considering the overall bird population is declining. The journal Science recently reported that the bird population is down more than 3 billion since 1970.

Northwestern is no stranger to the problem.

“Many of these buildings are pretty hazardous for birds,” Prince said.

For one, the Ryan Athletic Center is nearly all windows – as is the Frances Searle Building. And the most dangerous building of all is the Kellogg School of Management Global Hub – which has reflective glass on the windows.

“It’s a complete mirror,” Prince said.

So when birds fly toward the Kellogg Building, they see more trees and nature instead of glass.

And the birds are no safer at night. Lights lure them into the glass too.

“You’ve got glass, you’ve got lights, and you’ve got the most birds that are passing through – and it is a recipe for disaster,” Prince said.

Northwestern finds 700 birds killed or injured each year – and that’s just the tip of the iceberg. That figure is only the birds the Chicago Bird Collision Monitors find.

“We get what we can find for the two hours that we’re out,” Prince said.

That’s why they created a solution. Putting patterns like small dots and strips on windows stops birds from smashing into them.

“Birds see something that they can’t fit through,” Prince said.

And since they’ve placed the patterns on some windows, Northwestern has seen results.

The Kellogg Global Hub was the most deadly building for birds on campus, accounting for 63 percent of all collisions.

After protective films were added to some windows, it’s down to 33 percent.

“So we know it works,” Prince said.

Bonnie Humphrey, the director of design at Northwestern, said the changes are better sooner rather than later.

“Architects should definitely consider it while they’re designing the building,” Humphrey said.

She said the campus’ newer buildings will incorporate such designs from the start, and encouraged the designers of city buildings to do the same.

“Chicago has some pretty spectacular architecture, and it’s just too bad that it’s harmful to birds,” Prince said.

The Chicago Bird Collision Monitors is expanding beyond Evanston. They are collaborating with other groups to pass an ordinance that would require new city buildings to have bird-safe windows.

Prince said it will drastically reduce bird deaths and make Chicago a more bird-friendly city.