NARRATOR：

Now listen to part of a lecture on the topic you just read about.

MALE PROFESSOR：

None of the solutions you’ve read about will effectively stop birds from getting injured.

First, replacing regular glass with one-way glass.

Well, the problem with one-way glass is that to the bird on the outside, a one-way glass surface reflects just like a mirror.

And a surface that reflects like a mirror is just as bad as regular glass for birds because birds don’t understand mirrors.

If they see a reflection of the sky in a mirror or of a tree in a mirror, they think the refection is the sky or is the tree, and they’ll fly right into them.

The second solution—painting colorful patterns like stripes on regular glass—also has problems.

As the reading said, these designs include openings so people inside the buildings can see out.

But birds will perceive these unpainted openings as open holes.

And if birds think that they’re seeing holes, they will try to fly right through them.

To prevent birds from doing this, the unpainted spaces in a window would have to be extremely small.

But that would then make the rooms of the buildings too dark for the people inside them.

The third solution, creating an artificial magnetic field, won’t work very well either.

While it’s true that birds use Earth’s magnetic field to help them navigate, they use this only when they’re traveling very long distances.

For example, if a bird is migrating from a cold country to a warm one before winter, it will use its magnetic sense to figure out which way it should fly.

But this ability isn’t used to go over short distances, such as going from one side of the city to another.

For short trips, birds use their eyes and the brightness of light to determine where to go.

So magnetic signals from buildings won’t have much effect.