Some comments about a very interesting account that just appeared on
Tweeters, thanks to Dan Victor.

When migration begins again in the autumn, the slightly larger
Greenland wheatears become quite common for a while in Britain.
What is strange is that these birds, which went off in the direc-
tion of Canada, and those that went in the other direction to Si-
beria, both return to Europe, and only then turn south, back down
the route they went up by. It would make far more sense for the
first group to winter in Central America, and for the second
group to winter in Southern Asia.

No, it doesn't make sense for wheatears to migrate to Central America or
Southern Asia, which are full of rain forests. Modern-day bird migration
originated (or continued) when the last glaciers withdrew only 10,000 years
ago, allowing plants and animals to colonize the higher latitudes. These
birds were already spending the winter in habitats optimal to them, and it
makes all the sense in the world for them to return to them, no matter
where they go to breed.

As the author of the document wrote, their evolutionary history is significant.

Dennis Paulson, Univ. of Puget Sound