| 1. |
- Eikenaar, Cas, et al.
(författare)
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Recovery of constitutive immune function after migratory endurance flight in free-living birds
- 2023
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Ingår i: Biology letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 19:2
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Tidskriftsartikel (refereegranskat)abstract
- Strenuous physical activity can negatively affect constitutive innate immune function (CIF), the always present first line of defence against pathogens. CIF is non-specific, and thus vital when encountering novel pathogens. A lowered CIF likely increases the risk of infection and disease. Migratory birds engage in truly extreme physical activity during their endurance flights, however, little is known about how they deal with the negative impact this has on their immune function. By collecting both between- and within-individual data we show, for the first time, that free-flying migratory birds can recover several parameters of CIF during stopovers, which are stationary periods in between migratory flights. With this, we provide an important piece of the puzzle on how migrating birds cope with the physiological challenges they face on their biannual journeys. Furthermore, our study stresses the importance of migratory stopovers beyond fuel accumulation.
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| 2. |
- Eikenaar, Cas, et al.
(författare)
-
Stopovers Serve Physiological Recovery in Migratory Songbirds
- 2023
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Ingår i: Physiological and Biochemical Zoology. - 1522-2152. ; 96:5, s. 378-389
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Tidskriftsartikel (refereegranskat)abstract
- Migrating birds perform extreme endurance exercise when fly-ing. 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 accumulat-ing 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.
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