Migrations: Which Came First, North- or South-bound Migration?

Every year, hundreds of bird species migrate between North and South America. Some species likely evolved from ancestors that moved north in search of new breeding habitats: the “southern home” hypothesis. But others may have extended their winter ranges south: the “northern home” hypothesis. Many birds have likely gained and lost the ability to migrate multiple times over the course of evolution. And it’s still happening today.

More info and transcript at BirdNote.org. 

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