Thanks PETTIFOGGER, interesting article on the bar-tailed godwit.
I see that the flight averaged 34.8 mph and took 8.5 days non-stop at elevations between 3,000 m (9,843 ft) and 4,000 m (13,123 ft), where the temperature would have been between 30ºF (-1ºC) and 12ºF (-11ºC), and that the bird carried a satellite transmitter and batteries lasting the return journey!
So not so cold, but still pretty chilly for both the bird and the batteries, being cold-soaked for 8+ days.
