This is Bird Note.

The bobbling may just be the happiest bird of spring.

There's such delight in the bobbling's bubbly, jangling song.

As bobblings return to North America from the tropics each spring,

they have good reason to sing with joy.

The two ounce birds have completed one of the longest migrations of any songbird,

roughly 6,000 miles.

Bobbling's fly from Argentina all the way to the northern states and Canada.

How do they manage to cross all that hazardous terrain and hundreds of miles of open water?

Like many birds, bobblings rely on cues from the stars and sun,

and are guided by landmarks like rivers and mountain ranges.

But bobbling's also have an ace up their sleeve.

Like some other migratory birds, they can sense the Earth's magnetic field.

There are tiny quantities of the mineral magnetite deep in the bobbling's nasal tissues.

It makes the bobbling's beak a kind of built-in compass.

By the time it reaches 9 years old, one of these epic voyagers will have flown a distance equivalent

to four and a half times around the Earth.

For Bird Note, I'm Mary McCann.