Every year in the United States as many as a billion birds die while migrating.

It's not due to climate change or some toxic substance in the air or water.

This culprit is hiding in plain sight. The birds are killed when they collide with

glass. For the latest in our saving species series, we want to see an effort to

reduce this carnage in Philadelphia, where it turns out residents love a lot more

birds than just the eagles.

And so the birds are attracted to the brightness.

The sun is barely up over downtown Philadelphia and the guy known as the bird man is already at work.

Stephen Machiaevsky is a fixture here during the spring and fall migrations, looking for birds not in the skies but on the sidewalks where

they've fallen after hitting a window. Some are dead, some are injured, others just

stunned. They don't know what glass is. They don't know glass is hard. They just see a reflection or they think they can go in or through and then they start hitting.

It didn't take long for Machiaevsky's eagle eyes to spot a dead oven bird a small songbird.

So beautiful. They have this orange crown and they have this loud voice singing

teacher teacher teacher.

The species and other details go into his logbook.

The dead bird goes into a plastic bag

to be taken to a lab for study.

The all-too-common routine done, he moves on. Machiaevsky's a volunteer for bird-safe filling, a partnership aimed at creating safe spaces for birds.

Since 1970, the United States and Canada have seen a decline in bird species of 30%.

While much of it's due to habitat loss,

glass windows pose the third largest threat.

Robin Erosari is with Audubon Mid-Atlantic.

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