Birds don't get the respect that they deserve. Maybe they just don't inculcate the fear that some mammals, reptiles, and sharks inspire. They are hard to cuddle up to, and only one of them (the cassowary) legitimately inspires fear in Man.
The world of birds is nature red in beak and talon instead of tooth and claw, but you have to hand it to them: they are beautiful, and with the arguable exceptions of some sea creatures and (only recently) us, they have the longest, swiftest, and most heroic migrations. It's all for survival: getting food where it is available for only part of the year and escaping predators that find chicks easy prey. Birds don't have it easy; Darwinian natural selection treats exhausted, ill, or injured birds with supreme harshness. Add to that the perils that Man has imposed upon them: the firearm and trained dog (cats aren't shown; we know them all too well), poaching for the wildlife trade, and environmental pitfalls. You want to do anything to keep the geese from flying into a Soviet-era industrial complex that reminds one of a portal to Hell, a place unfit for humans but especially hazardous to birds.
You will feel tragedy for the wader bird with a broken wing that faces an army of hungry crabs and cheer for a macaw that tries to open its own cage to escape the pet trade. Although a documentary, this film shows harsh drama and heroism, the latter without resorting to Disney-esquire anthropomorphism.
The flight sequences are magnificent -- so good that they look almost unreal. Maybe it's the unusual camera angles, such as seeing birds from the sides in a more genuine "bird's eye view". If there is a lot of bird flight, (1) it's a lot of different birds, and (2) what do you expect of migratory birds? For a more encyclopedic treatment of bird behavior on film, then turn to Attenborough's "Secret Life of Birds".
The only special effects, that of imposing migrant birds over a globe, are ludicrous. Mercifully one sees little of that, and it has its purpose: to establish the incredible distances that some birds fly. Special effects are not necessary: we see some flights through some spectacular vistas -- at boat level in Paris and at the level of bird flight in New York City, the Great Wall of China, Mount Kilomanjaro, the Grand Canyon and Monument Valley.
Some of the urban flight scenes could never be made again; the World Trade Center buildings, destroyed by the most perverse sort of flying imaginable, created a backdrop that could never be seen again. Governments may make urban flights such as that through New York with the birds impossible. We just might never get to see scenes in a sequel in which migratory birds fly through San Francisco, Rio de Janeiro, Rome, Beijing, St. Petersburg (Russia), or past the Hagia Sophia, the Pyramids, or the Taj Mahal.
