This is Bird Note.

Hollow bones help birds like this herring goal,

sail around in the air without using much energy.

But goals resting on the water look remarkably different

from the common loon floating nearby.

A goal's body rides high above the surface, like a cork,

while the loons back just tops above the water,

like a submarine peeking above the waves.

That's because these two birds are specialized

for very different lifestyles.

While the goal is adapted for efficient flight,

the loon is fine tuned for the underwater world.

The loons bones are denser than those of goals,

songbirds, and other expert flyers.

With a lightweight skeleton, they'd be too buoyant

to dive and chase fish.

Instead, loons can kick their powerful legs and webbed feet

to swim 200 feet or more underwater.

Penguins can dive even deeper.

Emperor penguins submerge for up to 30 minutes

and can reach depths of 1500 feet before coming up for air.

Dense bodies make these birds poor flyers

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