Oxidative state is associated with migration distance, but not traits
linked to flight energetics
Abstract
Flight can be highly-energy demanding, but its efficiency depends
largely on flight style, wing shape and loading, and a range of
morphological and lifestyle adaptations that can modify the cost of
sustained flight. Such behavioural and morphological adaptations can
also influence the physiological costs associated with migration. For
instance, during intense flight and catabolism of reserves, lipid damage
induced by pro-oxidants increases, and to keep oxidative physiological
homeostasis under control, the antioxidant machinery is upregulated.
Studies on the oxidative physiology of endurance flight have produced
contradictory results, making generalization difficult, especially
because multispecies studies are missing. Therefore, to explore the
oxidative cost of flight and migration, we explored the association
between three measures of the antioxidant capacity (total antioxidant
status, uric acid and glutathione concentration) and one measure of
oxidative damage of lipids (malondialdehyde) with variables reflecting
flight energetics (year-round or specifically during migration) across
113 European bird species using a phylogenetic framework. We found that
none of the traits predicting year-round flight energy expenditure,
including flight style, wing morphology and flight muscle morphology
explained any measures of oxidative state measured during the energy
demanding breeding period, suggesting that birds endure their everyday
exercise without or low oxidative cost. However, oxidative damage to
lipids and one component of the endogenous antioxidant system (uric
acid), measured after the end of spring migration on breeding adult
birds, increased with migration distance. Our results suggest that
migration might have oxidative consequences that are carried over to
subsequent life history stages (breeding).