Bartailed godwits fly 29-thousand kilometres a year between their Christchurch feeding grounds to breed in the Arctic tundra - the longest known non-stop migration for any bird.
Arctic terns also travel massive distances and swifts spend 80 percent of their lives on the wing - even sleeping airborne.
In our occasional series, I Didn't Know That, Massey University's School of Agriculture associate professor, Phil Battley is a expert in long-distance migration and explains how they do it.
