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 loon's back just tops above the water, like a submarine peaking 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 loon's 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 1,500 feet before coming

up for air.

Dense bodies make these birds poor flyers, or even flightless in the case of penguins.

But they are acrobats under the waves.

For bird note, I'm Ariana Rimmel.