Can differential fatty acid composition help migrating birds to limit oxidative lipid damage?

BLOOD FATTY ACID PROFILES IN CHILEAN (PHOENICOPTERUS CHILENSIS) AND CARIBBEAN (PHOENICOPTERUS RUBER) FLAMINGOS IN MANAGED CARE

Flamingos in managed care are vulnerable to inflammatory states, including pododermatitis, trauma, and capture myopathy. Fatty acids are an important component of well-balanced nutrition and crucial to endogenous immune responses associated with these conditions, yet fatty acids have not been assessed in flamingos. This study reported complete whole blood circulating fatty acid profiles in two flamingo species in managed care receiving different diets. Whole blood from Chilean flamingos (Phoenicopterus chilensis) (n=16) and Caribbean flamingos (Phoenicopterus ruber) (n=17) was collected during routine exams and prepared on blood spot cards for complete fatty acid profile analysis in which 24 individual fatty acids, nine fatty acids groups, and four calculated parameters were quantifiable. Non-parametric statistical analysis compared profiles between species, and between sex of Chilean flamingos. The median ratio of omega-6/omega-3 fatty acids was 5.64. Chilean flamingos had significantly (P<0.05) higher percentages of 11 individual fatty acids, total polyunsaturated and highly unsaturated fatty acids, total omega-3 and omega-6 fatty acids, arachidonic acid (AA; 20:4w6)/eicosapentaenoic acid (EPA; 20:5w3) ratio, and total EPA + DHA, whereas Caribbean flamingos had significantly (P<0.05) higher percentages of eight individual fatty acids, and total saturated fatty acids. Male Chilean flamingos had significantly (P<0.05) higher percentages of AA, EPA, and total polyunsaturated fatty acids, whereas females had significantly (P<0.05) higher oleic acid (18:1w9), total monounsaturated fatty acids, and total omega-9 fatty acids. Differences reported are highly attributable to variability in diet, although differences in fatty acid synthesizing pathways and hormonal influences may also play a role. This novel fatty acid data set in healthy flamingos is a valuable reference for complete health evaluations in managed care settings. Further comparisons with controlled diets and inclusion of free-ranging animals may enhance clinical utility.

Stopovers Serve Physiological Recovery in Migratory Songbirds

AbstractMigrating birds perform extreme endurance exercise when flying. This shifts the balance between the production of reactive oxygen species and the antioxidant defense system toward the former, potentially generating oxidative damages. In between migratory flights, birds make stopovers, where besides accumulating fuel (mainly fats), they are assumed to rest and recover from the strenuous flight. We performed a series of studies on both temporarily caged (northern wheatears) and free-flying (northern wheatears and European robins) migrants to investigate whether migrants recover during stopover by decreasing the amount of oxidative lipid damage (malondialdehyde [MDA]) and/or increasing the total nonenzymatic antioxidant capacity (AOX). In caged wheatears, MDA decreased within a single day. These birds were able to simultaneously accumulate considerable amounts of fuel. Also, in the free-flying wheatears, there was a decrease in MDA during stopover; however, this process seemed incompatible with refueling. The reason for this difference could relate to constraints in the wild that are absent in caged birds, such as food limitation/composition and locomotor activity. In the robins, there was a near significant decrease in MDA concentration in relation to how long the birds were already at stopover, suggesting that this species also physiologically recovers during stopover. AOX did not change during stopover in either of the wheatear studies. For the robins, however, uric acid-corrected AOX declined during stopover. Our results show that during stopover, migrating birds rapidly reduce oxidative lipid damage, thereby likely recovering their physiological state. In addition to the commonly accepted function of refueling, stopovers thus probably serve physiological recovery.

The oxidative balance and stopover departure decisions in a medium- and a long-distance migrant

BACKGROUND

Birds have extremely elevated metabolic rates during migratory endurance flight and consequently can become physiologically exhausted. One feature of exhaustion is oxidative damage, which occurs when the antioxidant defense system is overwhelmed by the production of damaging reactive oxygen species (ROS). Migrating birds have been shown to decrease the amount of oxidative lipid damage during stopovers, relatively stationary periods in between migratory flights. It has therefore been argued that, in addition to accumulating fuel, one of the functions of stopover is to restore the oxidative balance. If this is so, we would expect that migrating birds are unlikely to resume migration from stopover when they still have high amounts of lipid damage.

METHODS

To test this hypothesis, we measured parameters of the oxidative balance and related these to stopover departure decisions of song thrushes (Turdus philomelos) and northern wheatears (Oenanthe oenanthe), a medium- and long-distance songbird migrant, respectively. We measured malondialdehyde (MDA) concentration, a biomarker for oxidative lipid damage, and total non-enzymatic antioxidant capacity (AOX), an overall biomarker of protection against ROS. Stopover departure decisions were determined using a fully automated telemetry system set-up on our small island study site.

RESULTS

The decision to resume migration was not related with MDA concentration in either study species, also not when this was corrected for circulating fatty acid concentrations. Similarly, AOX did not affect this decision, also not when corrected for uric-acid concentration. The time within the night when birds departed also was not affected by MDA concentration or AOX. However, confirming earlier observations, we found that in both species, fat individuals were more likely to depart than lean individuals, and fat northern wheatears departed earlier within the night than lean conspecifics. Northern wheatears additionally departed earlier in spring with more southerly winds.

CONCLUSIONS

We found no support for the idea that stopovers departure decisions are influenced by parameters of the oxidative balance. We discuss possible reasons for this unexpected finding.