Birds are an incredibly diverse animal group. This is reflected in their physiology, as you can see in this short list of facts about the stamina and endurance ability of birds.
Coldest average temperature regularly endured by a bird: -50º F (-45.6º C) by Emperor Penguins on the Antarctic ice sheet.
Coldest temperature endured by a bird: -80.5º F (-62.5º C) by Snowy Owls in the Arctic.
Coldest temperature of land where a bird has been recorded: -129º F (-89.6º C) in Vostok, Russia, for the South Polar Skua.
Warmest temperature regularly endured by a bird: 111º to 113º F (44º to 45º C) by Larks and Wheatears.
Fastest running bird: the Ostrich, at 60 mph (97.5 km/h).
Fastest running bird which can also fly: the Greater Roadrunner, at 26 mph (42 km/h)
Longest-lived wild bird: a Royal Albatross, which has lived to over 58 years.
Longest-lived captive bird: a Sulfur-crested Cockatoo, which survived over 80 years.
Source of these facts: The Bird Almanac, by Dr. David M. Bird