I managed to find this program on my local PBS TV station. It is not a subject that I would normally seek out but now, having watched it, I am glad I did. It is a world of bird migration I had never actually focused on before.
My main knowledge of bird migration are the Hummingbirds, twice a year they migrate between North America and Central America, which is a pretty big trip for a little bird that weighs about the same as a USA nickel coin. As they fly nonstop over the Gulf of Mexico they can deplete up to one-half their weight during the 20-hour flight.
This documentary focuses on larger birds, they typically fly a distance then land to refuel before taking off again. But their total migration may be several thousands of miles. One bird was to migrate to Northern Russia and it was while the Russian invasion of Ukraine was in progress (still is, now in 2024) and the bird-chasers were not able to go all the way to verify their arrivals.
Many of the birds are trapped and tagged, in such a way that they can be identified from a distance. So the bird-chasers are able to spot specific birds as they stop at locations along the way.
This is a good program, it illuminates a field that many of us usually pay no attention to.