CHICAGO, Aug. 4 (UPI) -- Whether birds migrate from the south to the north or vice versa seems like a matter of scientific semantics. But the origin and order of things has implications as to why birds started migrating in the first place. A new study suggests birds move mainly from the north to the south, undermining traditional theories.
Scientists have long assumed most birds that split time between North America and the tropics of South America began doing so as a way to avoid the competition for food and mating partners in warmer regions -- moving from the biologically diverse and overpopulated south to the quiet of the north.