| 1. |
- Eikenaar, Cas, et al.
(författare)
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Migrating birds rapidly increase constitutive immune function during stopover
- 2020
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Ingår i: Royal Society Open Science. - : The Royal Society. - 2054-5703. ; 7:2
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Tidskriftsartikel (refereegranskat)abstract
- Migratory flight is physiologically highly demanding and has been shown to negatively affect multiple parameters of constitutive immune function (CIF), an animal’s first line of physiological defence against infections. In between migratory flights, most birds make stopovers, periods during which they accumulate fuel for the next flight(s). Stopovers are also commonly thought of as periods of rest and recovery, but what this encompasses is largely undefined. Here, we show that during stopover, northern wheatears Oenanthe oenanthe, a long-distance migratory bird, can rapidly increase constitutive innate immune function. We caught and temporarily caged birds under ad libitum food conditions at a stopover site in autumn. Within 2 days, most birds significantly increased complement activity and their ability to kill microbes. Changes in immune function were not related to the birds’ food intake or extent of fuel accumulation. Our study suggests that stopovers may not only be important to refuel but also to restore immune function. Additionally, the increase in CIF could help migrating birds to deal with novel pathogens they may encounter at stopover sites.
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| 2. |
- Eikenaar, Cas, et al.
(författare)
-
Oxidative damage to lipids is rapidly reduced during migratory stopovers
- 2020
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 34:6, s. 1215-1222
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Tidskriftsartikel (refereegranskat)abstract
- Most migrating birds need to stopover in between flights in order to refuel. Lately, additional purposes of stopover have been suggested, including physiological recovery from metabolically demanding migratory flight. One apparently unavoidable, but harmful physiological effect of migratory flight is increased oxidative damage to lipids and proteins. We here, for the first time, tested whether migrating birds are able to reduce their oxidative damage during stopover. To be able to collect longitudinal data on a large number of individual birds, we temporarily caged wild northern wheatears, a long-distance migrant which does not suffer stress when caged during migration. Around noon on the first and third day at stopover, the birds were blood-sampled to determine malondialdehyde (MDA) concentration, a commonly used marker of oxidative damage to lipids. We found that MDA concentrations significantly decreased during stopover, a result unchanged when correcting for the peroxidizability of the substrate. The extent of the decrease was unrelated to the amounts of food consumed or of fuel accumulated. Our findings support the hypothesis that stopovers serve reduction of oxidative damage, warranting re-thinking of how birds accomplish their migrations. They also highlight the need to include physiological recovery as a driver of the (temporal) organization of migration. A free Plain Language Summary can be found within the Supporting Information of this article.
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| 3. |
- 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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| 4. |
- Eikenaar, Cas, et al.
(författare)
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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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