High altitude (HA; n = 5) chickens (Gallus gallus) with a high oxygen hemoglobin (Hb) affinity were transported from their birthplace (Puno, Peru 4,000 m) down to sea level (Lima, Peru). The in vivo whole blood oxygen affinity (P50) and the eggshell permeability (P) were studied after several months living at sea level and in the first (F1) and second (F2) generations born at sea level. Our approach was to analyze changes in Hb affinity and eggshell permeability, considered as indicators of HA adaptation in birds. Our results show an increase of the P50 values (a decrease in Hb affinity) towards sea-level values. The results in P indicate that this variable increases towards sea level values in the F2 generation. We conclude that in the Andean chicken, a relative 'newcomer' to high altitude (no more than 500 years), neither the Hb affinity for oxygen nor the eggshell permeability are invariable indicators of HA adaptation, in contrast with other native high altitude mammals and birds.