Regarding 1, wikipedia about Rüppell's vulture (highest-flying bird) explains the adaptation: "The birds have a specialized variant of the hemoglobin alphaD subunit; this protein has a great affinity for oxygen, which allows the species to absorb oxygen efficiently despite the low partial pressure in the upper troposphere. A Rüppell's vulture was confirmed to have been ingested by a jet engine of an airplane flying over Abidjan, Ivory Coast on 29 November 1973 at an altitude of 11,300 m (37,000 ft)." https://en.wikipedia.org/wiki/R%C3%BCppell%27s_vulture