Markers of the oxidative balance may show diurnal variation and differ between the sexes (e

Markers of the oxidative balance may show diurnal variation and differ between the sexes (e.g., Jenni-Eiermann et?al. et?al. 2008). Jenni-Eiermann et?al. (2014) found that European robins caught out of nocturnal migratory flight had higher oxidative damage to proteins than birds resting during the day, despite that the flying birds also had higher enzymatic antioxidant capacity. Finally, migrating Nathusius bats caught out of flight had higher oxidative damage than conspecifics resting for 18 or 24?h after having been caught (Costantini et?al. 2019). Taken together, the above studies indicate that migratory flight may compromise constitutive immune function and increase oxidative damage (but see Bairlein et?al. 2015). Yet, studies investigating both physiological systems within one migratory species are, to our best knowledge, lacking. To fuel migratory flight birds store large quantities of energy, mainly in the form of fat (95%), and some as protein (Jenni and Jenni-Eiermann 1998). As most migrants cannot reach their final destination in one direct flight, they have to land and replenish their energy stores during so-called stopovers. Energy stores of migrants at stopover normally vary widely within a given species (e.g., Salewski and Schaub 2007), and some individuals may even arrive with fully depleted stores. The energetic condition of a migrant at stopover depends on the energy stores at departure on the flight preceding the stopover, KRAS G12C inhibitor 16 the energetic KRAS G12C inhibitor 16 demands of that flight, and the amount of energy accumulated (or lost) after landing at the Rabbit Polyclonal to SRF (phospho-Ser77) stopover site. Although the relative contributions of these three factors to migrants energy stores at stopover are unknown, part of the variation in energy stores among migrants of a given species will be attributable to variation in the energetic demands of the flight preceding the stopover, especially when birds are caught relatively soon after their arrival. Hence, the physiological condition of migrants at stopover may be expected to depend, in part, on their energy stores. This expectation does not only follow from flight draining energy stores, but also from the idea that when accumulating energy at stopover, migrants possibly recover their physiological condition. Owen and Moore (2008) found that in migrants temporarily caged at stopover, immune response to phytohemagglutinin was positively related to change in mass, suggesting that immune function KRAS G12C inhibitor 16 may improve during stopover. At the population level, Skrip et?al. (2015) found that oxidative damage to lipids decreased with the time migrants had spent at stopover before being caught and sampled, i.e., with the time birds were (potentially) refueling. Estimating energetic condition of migrants at stopover is standard practice. However, studies testing the expectation that the physiology of migrants is related to their energetic condition are scarce, and results are mixed. For example, where Owen and Moore (2008) did find relationships between migrants energy stores and absolute leukocyte counts, Cornelius et?al. (2014) found little evidence for such relationships. Similarly, estimates of energy stores have been found to be negatively (Jenni-Eiermann et?al. 2014), positively (Skrip et?al. 2015), or not (Costantini et?al. 2007) correlated with oxidative damage. Furthermore, to our best knowledge, no study has measured the relationships between energy stores, immune function and oxidative damage in the same migrant species. In the current study, we related energy stores of northern wheatears ((BKA), and haptoglobin-like activity (Hp)], and one parameter of constitutive acquired immune function (total immunoglobulins, IgY). To assess the birds oxidative state, we measured total non-enzymatic antioxidant capacity (AOX) and malondialdehyde (MDA) level. The measure of nonenzymatic AOX is a reliable and general (non-specific) marker of antioxidant capacity of plasma, thus it provides a good overall marker of protection against reactive oxygen species (ROS) compared to specific assays of individual antioxidants. MDA is a frequently used biomarker of current and rapid oxidative damage to lipids, thus in this context.