Migratory flight is an intensive exercise that requires birds to maintain high aerobic capacities for many hours or days. Maintaining oxygen supply to flight muscles is therefore important during migration, especially since tracking studies have shown that songbirds will ascend to altitudes of 6,000 m during migratory flight where oxygen is less readily available (hypoxia). Whether there are adaptations or seasonal plasticity along the oxygen cascade and hypoxic chemoreflex that allow songbirds to fly at such high altitudes during the migratory season is unknown. Research during my postdoc has shown that migratory songbirds exhibit seasonal plasticity along the oxygen cascade which enhance oxygen uptake and movement to the flight muscle during migration. This includes changes in breathing pattern, haemoglobin-oxygen binding affinity, and muscle fiber size and phenotype. We have also shown that the magnitude of seasonal plasticity may be dictated by migratory distance and/or whether the songbird species is migratory or resident. Additionally, in yellow-rumped warblers there appears to be a blunted hypoxic chemoreflex in response to flight at high altitude (~3,000 m above sea level). Measurements of adrenaline concentration increased with flight, but were not significantly higher when flight was conducted at high altitude. Together, these findings show that songbirds exhibit seasonal plasticity along the oxygen cascade which would be important for maintain oxygen movement to the flight muscle during high altitude flight.