| 1. |
- Adamik, Peter, et al.
(författare)
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Barrier crossing in small avian migrants : individual tracking reveals prolonged nocturnal flights into the day as a common migratory strategy
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Over decades it has been unclear how individual migratory songbirds cross large ecological barriers such as seas or deserts. By deploying light-level geolocators on four songbird species weighing only about 12 g, we found that these otherwise mainly nocturnal migrants seem to regularly extend their nocturnal flights into the day when crossing the Sahara Desert and the Mediterranean Sea. The proportion of the proposed diurnally flying birds gradually declined over the day with similar landing patterns in autumn and spring. The prolonged flights were slightly more frequent in spring than in autumn, suggesting tighter migratory schedules when returning to breeding sites. Often we found several patterns for barrier crossing for the same individual in autumn compared to the spring journey. As only a small proportion of the birds flew strictly during the night and even some individuals might have flown non-stop, we suggest that prolonged endurance flights are not an exception even in small migratory species. We emphasise an individual’s ability to perform both diurnal and nocturnal migration when facing the challenge of crossing a large ecological barrier to successfully complete a migratory journey.
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| 2. |
- Briedis, Martins, et al.
(författare)
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A full annual perspective on sex-biased migration timing in long-distance migratory birds
- 2019
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 286:1897
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Tidskriftsartikel (refereegranskat)abstract
- In many taxa, the most common form of sex-biased migration timing is protandry – the earlier arrival of males at breeding areas. Here we test this concept across the annual cycle of long-distance migratory birds. Using more than 350 migration tracks of small-bodied trans-Saharan migrants, we quantify differences in male and female migration schedules and test for proximate determinants of sex-specific timing. In autumn, males started migration about 2 days earlier, but this difference did not carry over to arrival at the non-breeding sites. In spring, males on average departed from the African non-breeding sites about 3 days earlier and reached breeding sites ca 4 days ahead of females. A cross-species comparison revealed large variation in the level of protandry and protogyny across the annual cycle. While we found tight links between individual timing of departure and arrival within each migration season, only for males the timing of spring migration was linked to the timing of previous autumn migration. In conclusion, our results demonstrate that protandry is not exclusively a reproductive strategy but rather occurs year-round and the two main proximate determinants for the magnitude of sex-biased arrival times in autumn and spring are sex-specific differences in departure timing and migration duration.
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| 3. |
- Briedis, Martins, et al.
(författare)
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Breeding latitude leads to different temporal but not spatial organization of the annual cycle in a long-distance migrant
- 2016
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Ingår i: Journal of Avian Biology. - : Wiley. - 0908-8857 .- 1600-048X. ; 47:6, s. 743-748
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Tidskriftsartikel (refereegranskat)abstract
- The temporal and spatial organization of the annual cycle according to local conditions is of crucial importance for individuals' fitness. Moreover, which sites and when particular sites are used can have profound consequences especially for migratory animals, because the two factors shape interactions within and between populations, as well as between animal and the environment. Here, we compare spatial and temporal patterns of two latitudinally separated breeding populations of a trans-Equatorial passerine migrant, the collared flycatcher Ficedula albicollis, throughout the annual cycle. We found that migration routes and non-breeding residency areas of the two populations largely overlapped. Due to climatic constraints, however, the onset of breeding in the northern population was approximately two weeks later than that of the southern population. We demonstrate that this temporal offset between the populations carries-over from breeding to the entire annual cycle. The northern population was consistently later in timing of all subsequent annual events - autumn migration, non-breeding residence period, spring migration and the following breeding. Such year-round spatiotemporal patterns suggest that annual schedules are endogenously controlled with breeding latitude as the decisive element pre-determining the timing of annual events in our study populations.
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| 4. |
- Briedis, Martins, et al.
(författare)
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Broad-scale patterns of the Afro-Palaearctic landbird migration
- 2020
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Ingår i: Global Ecology and Biogeography. - : WILEY. - 1466-822X .- 1466-8238. ; 29:4, s. 722-735
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Knowledge of broad-scale biogeographical patterns of animal migration is important for understanding ecological drivers of migratory behaviours. Here, we present a flyway-scale assessment of the spatial structure and seasonal dynamics of the Afro-Palaearctic bird migration system and explore how phenology of the environment guides long-distance migration.Location: Europe and Africa.Time period: 2009-2017.Major taxa studied: Birds.Methods: We compiled an individual-based dataset comprising 23 passerine and near-passerine species of 55 European breeding populations, in which a total of 564 individuals were tracked during migration between Europe and sub-Saharan Africa. In addition, we used remotely sensed primary productivity data (the normalized difference vegetation index) to estimate the timing of vegetation green-up in spring and senescence in autumn across Europe. First, we described how individual breeding and non-breeding sites and the migratory flyways link geographically. Second, we examined how the timing of migration along the two major Afro-Palaearctic flyways is tuned with vegetation phenology at the breeding sites.Results: We found the longitudes of individual breeding and non-breeding sites to be related in a strongly positive manner, whereas the latitudes of breeding and non-breeding sites were related negatively. In autumn, migration commenced ahead of vegetation senescence, and the timing of migration was 5-7 days earlier along the Western flyway compared with the Eastern flyway. In spring, the time of arrival at breeding sites was c. 1.5 days later for each degree northwards and 6-7 days later along the Eastern compared with the Western flyway, reflecting the later spring green-up at higher latitudes and more eastern longitudes.Main conclusions: Migration of the Afro-Palaearctic landbirds follows a longitudinally parallel leapfrog migration pattern, whereby migrants track vegetation green-up in spring but depart before vegetation senescence in autumn. The degree of continentality along migration routes and at the breeding sites of the birds influences the timing of migration on a broad scale.
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| 5. |
- Brlík, Vojtěch, et al.
(författare)
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Population-specific assessment of carry-over effects across the range of a migratory songbird
- 2020
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Ingår i: Behavioral Ecology and Sociobiology. - : Springer Science and Business Media LLC. - 0340-5443 .- 1432-0762. ; 74:12
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: Annual cycle events may be interlinked, influence following annual cycle stages, and may alter performance of individuals. Such links, called carry-over effects, can explain individual variation in timing or reproductive success in migratory species. Identifying the key links affecting fitness may reveal the mechanisms of species population dynamics but the current evidence for the strongest carry-over effects is equivocal. Here, we aim to assess the carry-over effects in great reed warblers Acrocephalus arundinaceus, a long-distance migratory songbird, using 103 full-annual tracks from three European and two Asian breeding populations. Our results showed strong positive relationships within autumn and spring migration periods and buffering capacity of the non-breeding period preventing events to carry over between these periods. Moreover, we found no profound relation between the non-breeding habitat quality or seasonality (quantified using stable isotopes and remote sensing data) and the timing of spring migration. The strongest carry-over effects occurred in individuals from the southern European breeding population compared to the northern and the central European populations. A moderate relationship between the habitat seasonality during moult and the spring migration timing indicates the importance of the complete moult. The overall weak carry-over effects of non-breeding habitat conditions found in this study contrast with previous results and imply between-species differences in these crucial relationships. Moreover, the population-specific carry-over effects highlight the importance of multi-population approach and advise caution in interpretation of results from single-population studies. Finally, the carry-over effect from the moulting period indicates the significance of a so-far neglected link in the species. Significance statement: Environmental conditions vary in space and time. Therefore, migratory species adjust the timing of migration in order to maximise their fitness. However, the links between annual cycle events in multiple populations and the consequences of environmental conditions outside the breeding range are scarcely known. In this study, we used tracking data of the great reed warbler, an insectivorous bird species breeding across western Eurasia and wintering in Africa, to study a complex system of links between annual events. We found that the strength of these links differed between geographically distinct populations but not between sexes. Moreover, harsh environmental conditions during moult delayed the timing of subsequent events. Our findings could help explain large-scale differences in population size changes observed in some species and highlight the importance of energetically demanding moult period for the life of migratory species. Finally, our results demonstrate the need for multi-population approach in studies on seasonal interactions.
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| 6. |
- Emmenegger, Tamara, et al.
(författare)
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Avian Haemosporidians Infecting Short- and Long-Distance Migratory Old World Flycatcher Species and the Variation in Parasitaemia After Endurance Flights
- 2023
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Ingår i: Acta Parasitologica. - 1230-2821. ; 68:4, s. 746-753
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Avian haemosporidians are widespread parasites, occurring in many bird families and causing pathologies ranging from rather benign infections to highly virulent diseases. The state of knowledge about lineage-specific intensities of haemosporidian infection (i.e., parasitaemia) is mainly based on infection experiments conducted under laboratory conditions. The levels and range of parasitaemia in natural host–parasite associations as well as their influencing factor remain largely unexplored. Methods: Thus, we explored the parasitaemia of four songbird species (i.e., European Robins, Black and Common Redstarts and Whinchats) during migration by screening individuals upon landing on an insular passage site after extensive endurance flights to (1) describe their natural host–parasite associations, (2) quantify parasitaemia and (3) explore potential host- and parasite-related factors influencing parasitaemia. Results: We found 68% of Whinchats to be infected with haemosporidians, which is more frequent than any other of the studied host species (30–34%). Furthermore, we confirmed that parasitaemia of Haemoproteus infections was higher than average Plasmodium infections. Median parasitaemia levels were rather low (parasite cells in 0.01% of hosts’ red blood cells) and varied largely among the different parasite lineages. However, we found four individuals hosting infections with parasitaemia higher than typical chronic infections. Conclusions: Based on the known transmission areas of the respective lineages, we argue that these higher intensity infections might be relapses of consisting infections rather than acute phases of recent primary infections.
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| 7. |
- Emmenegger, Tamara, et al.
(författare)
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Effects of blood parasite infections on spatiotemporal migration patterns and activity budgets in a long-distance migratory passerine
- 2021
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 11:2, s. 753-762
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Tidskriftsartikel (refereegranskat)abstract
- How blood parasite infections influence the migration of hosts remains a lively debated issue as past studies found negative, positive, or no response to infections. This particularly applies to small birds, for which monitoring of detailed migration behavior over a whole annual cycle has been technically unachievable so far. Here, we investigate how bird migration is influenced by parasite infections. To this end, we tracked great reed warblers (Acrocephalus arundinaceus) with multisensor loggers, characterized general migration patterns as well as detailed flight bout durations, resting times and flight heights, and related these to the genus and intensity of their avian haemosporidian infections. We found migration distances to be shorter and the onset of autumn migration to be delayed with increasing intensity of blood parasite infection, in particular for birds with Plasmodium and mixed-genus infections. Additionally, the durations of migratory flight bout were prolonged for infected compared to uninfected birds. But since severely infected birds and particularly birds with mixed-genus infections had shorter resting times, initial delays seemed to be compensated for and the timing in other periods of the annual cycle was not compromised by infection. Overall, our multisensor logger approach revealed that avian blood parasites have mostly subtle effects on migratory performance and that effects can occur in specific periods of the year only.
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| 8. |
- Hahn, Steffen, et al.
(författare)
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Short- and long-distance avian migrants differ in exercise endurance but not aerobic capacity
- 2022
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Ingår i: BMC Zoology. - : Springer Science and Business Media LLC. - 2056-3132. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Background: Migratory birds differ markedly in their migration strategies, particularly those performing short- versus long-distance migrations. In preparation for migration, all birds undergo physiological and morphological modifications including enlargement of fat stores and pectoral muscles to fuel and power their flights, as well as cardiovascular and biochemical adjustments that improve lipid and oxygen delivery and uptake by flight muscles. While the magnitude of these changes varies in relation to migration strategy, the consequence of these variations on aerobic performance is unknown. We tested whether the aerobic performance of four Old-world flycatcher species (Muscicapidae) varied according to migration strategy by comparing minimum resting metabolic rates (RMRmin), exercise-induced maximum metabolic rates (MMR), and exercise endurance times of short-distance and long-distance migratory birds. Results: As expected, RMRmin did not vary between short-distance and long-distance migrants but differed between the species within a migration strategy and between sexes. Unexpectedly, MMR did not vary with migration strategy, but MMR and blood haemoglobin content were positively related among the birds tested. Exercise endurance times differed substantially between migration strategies with long-distance migrants sustaining exercise for > 60% longer than short-distance migrants. Blood haemoglobin content had a significant positive effect on endurance among all birds examined. Conclusions: The lack of difference in RMRmin and MMR between long- and short-distance migrants during this stage of migration suggests that the attributes favouring the greater aerobic endurance of long-distance migrants did not come at the expense of increased maintenance costs or require greater aerobic capacity.
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| 9. |
- Hahn, Steffen, et al.
(författare)
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Spatially different annual cycles but similar haemosporidian infections in distant populations of collared sand martins
- 2021
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Ingår i: BMC Zoology. - : Springer Science and Business Media LLC. - 2056-3132. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundPopulations of long-distance migratory birds experience different environments and are consequently exposed to different parasites throughout their annual cycles. Though, specific whereabouts and accompanied host-parasite interactions remain unknown for most migratory passerines. Collared sand martins (Riparia riparia) breeding in the western Palaearctic spend the nonbreeding period in Africa, but it is not yet clear whether specific populations differ in overwintering locations and whether these also result in varying infections with vector-transmitted endoparasites.ResultsGeolocator tracking revealed that collared sand martins from northern-central and central-eastern Europe migrate to distant nonbreeding sites in West Africa and the Lake Chad basin in central Africa, respectively. While the ranges of these populations were clearly separated throughout the year, they consistently spent up to 60% of the annual cycle in Africa. Ambient light recorded by geolocators further indicated unsheltered roosting during the nonbreeding season in Africa compared to the breeding season in Europe.We found 5–26% prevalence of haemosporidian parasites in three breeding populations and one migratory passage population that was only sampled but not tracked. In total, we identified seven Plasmodium and nine Haemoproteus lineages (incl. two and seven new lineages, respectively), the latter presumably typical for swallows (Hirundinae) hosts. 99.5% of infections had a low intensity, typical for chronic infection stages, whereas three individuals (0.5%) showed high parasitaemia typical for acute infections during spring migration and breeding.ConclusionsOur study shows that blood parasite infections are common in several western Palaearctic breeding populations of collared sand martins who spent the nonbreeding season in West Africa and the lake Chad region. Due to long residency at the nonbreeding grounds blood parasite transmissions may mainly occur at host population-specific residences sites in Europe and Africa; the latter being likely facilitated by unsheltered roosting and thus high vulnerability to hematophagous insects. The rare cases of high parasitaemia during spring migration and breeding further indicates either relapses of chronic infection or primary infections which occurred shortly before migration and during breeding.
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| 10. |
- Jung, Christian, et al.
(författare)
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A comparison of very old patients admitted to intensive care unit after acute versus elective surgery or intervention
- 2019
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Ingår i: Journal of critical care. - : W B SAUNDERS CO-ELSEVIER INC. - 0883-9441 .- 1557-8615. ; 52, s. 141-148
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Tidskriftsartikel (refereegranskat)abstract
- Background: We aimed to evaluate differences in outcome between patients admitted to intensive care unit (ICU) after elective versus acute surgery in a multinational cohort of very old patients (80 years; VIP). Predictors of mortality, with special emphasis on frailty, were assessed.Methods: In total, 5063 VIPs were induded in this analysis, 922 were admitted after elective surgery or intervention, 4141 acutely, with 402 after acute surgery. Differences were calculated using Mann-Whitney-U test and Wilcoxon test. Univariate and multivariable logistic regression were used to assess associations with mortality.Results: Compared patients admitted after acute surgery, patients admitted after elective surgery suffered less often from frailty as defined as CFS (28% vs 46%; p < 0.001), evidenced lower SOFA scores (4 +/- 5 vs 7 +/- 7; p < 0.001). Presence of frailty (CFS >4) was associated with significantly increased mortality both in elective surgery patients (7% vs 12%; p = 0.01), in acute surgery (7% vs 12%; p = 0.02).Conclusions: VIPs admitted to ICU after elective surgery evidenced favorable outcome over patients after acute surgery even after correction for relevant confounders. Frailty might be used to guide clinicians in risk stratification in both patients admitted after elective and acute surgery.
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