Swifts eat insects on the wing, so they must migrate to warmer climates every fall. The mystery has to do with where they spend the winter, because they've never been observed in the winter months. That's right, never! The black swift is the last North American bird species to have its wintering grounds remain unknown.
|Winter habitat in the Amazon rainforest|
The same research has not been done on swifts in the Canadian Rockies, so who knows if our swifts winter in the same place as their Colorado brethren, but if they do, that would add about 2000 km to the trip!
So we have a mystery solved, but a sense of wonder enhanced. If you'd like to get a fuller account of the story, try this wonderful post at the earbirding blog: