This sweet voice belongs to the Purple Martin, the largest swallow in the United States and Canada.

It's also one of our most beloved birds, judging by how many people put up nest boxes for them.

By October, nearly all the Purple Martins that spent the spring and summer visiting North America to breed are headed back south a long way south.

In the fall, large flocks of Martins end up all the way down in the Amazon Basin, and some will continue even farther

south from there.

Purple Martins from Western North America will go all the way to southeastern Brazil, traveling

more than 5,000 miles in both spring and fall.

But why travel so far each year?

Scientists believe that Purple Martins were first a South American swallow species.

Over time, they evolved a seasonal migration to North America

because the longer days of summer sunlight provided extra hunting and feeding opportunities

during nesting season.

This same evolutionary pattern

likely applies to many of the other tropical migrating songbirds

that make their way north and south on their epic journeys each year.

For Bird Note, I'm Ashley Ahern.

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