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- Alerstam, Thomas, et al.
(författare)
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Long-distance migration: evolution and determinants
- 2003
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 103:2, s. 247-260
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Tidskriftsartikel (refereegranskat)abstract
- Long distance migration has evolved in many organisms moving through different media and using various modes of locomotion and transport. Migration continues to evolve or become suppressed as shown by ongoing dynamic and rapid changes of migration patterns. This great evolutionary flexibility may seem surprising for such a complex attribute as migration. Even if migration in most cases has evolved basically as a strategy to maximise fitness in a seasonal environment, its occurrence and extent depend on a multitude of factors. We give a brief overview of different factors (e.g. physical, geographical, historical, ecological) likely to facilitate and/or constrain the evolution of long distance migration and discuss how they are likely to affect migration. The basic driving forces for migration are ecological and biogeographic factors like seasonality, spatiotemporal distributions of resources, habitats, predation and competition. The benefit of increased resource availability will be balanced by costs associated with the migratory process in terms of time (incl. losses of prior occupancy advantages), energy and mortality (incl. increased exposure to parasites). Furthermore, migration requires genetic instructions (allowing substantial room for learning in some of the traits) about timing, duration and distance of migration as well as about behavioural and physiological adaptations (fuelling, organ flexibility, locomotion, use of environmental transport etc) and control of orientation and navigation. To what degree these costs and requirements put constraints on migration often depends on body size according to different scaling relationships. From this expos it is clear that research on migration warrants a multitude of techniques and approaches for a complete as possible understanding of a very complex evolutionary syndrome. In addition, we also present examples of migratory distances in a variety of taxons. In recent years new techniques, especially satellite radio telemetry, provide new information of unprecedented accuracy about journeys of individual animals, allowing re-evaluation of migration, locomotion and navigation theories.
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| 2. |
- Barta, Z, et al.
(författare)
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Annual routines of non-migratory birds: optimal moult strategies
- 2006
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 112:3, s. 580-593
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Tidskriftsartikel (refereegranskat)abstract
- In a periodically changing environment it is important for animals to properly time the major events of their life in order to maximise their lifetime fitness. For a non-migratory bird the timing of breeding and moult are thought to be the most crucial. We develop a state-dependent optimal annual routine model that incorporates explicit density dependence in the food supply. In the model the birds' decisions depend on the time of year, their energy reserves, breeding status, experience, and the quality of two types of feathers (outer and inner primaries). Our model predicts that, under a seasonal environment, feathers with large effects on flight ability, higher abrasion rate and lower energetic cost of moult should be moulted closer to the winter (i.e. later) than those with the opposite attributes. Therefore, we argue that the sequence of moult may be an adaptive response to the problem of optimal timing of moult of differing feathers within the same feather tract. The model also predicts that environmental seasonality greatly affects optimal annual routines. Under high seasonality birds breed first then immediately moult, whereas under low seasonality an alternation occurs between breeding and moulting some of the feathers in one year and having a complete moult but no breeding in the other year. Increasing food abundance has a similar effect.
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| 3. |
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| 4. |
- Jonzén, Niclas, et al.
(författare)
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Climate patterns and the stochastic dynamics of migratory birds
- 2002
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 97:3, s. 329-336
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Tidskriftsartikel (refereegranskat)abstract
- We analyse time series data of 17 bird species trapped at Ottenby Bird Observatory, Sweden, during spring migration 1972-1999. The species have similar demography but respond differently to variation in the North Atlantic Oscillation (NAO) - a strong determinant of winter climate in the northern Hemisphere. Species wintering in northern Europe, compared to species having winter quarters in the Mediterranean area, tend to respond positively to variation in NAO. The variation within each group is high due to wide-ranging winter-distribution in many species, probably smoothing out the effect of spatial variation in NAO. Whereas mild winters (high NAO) are benign for many - but not all - birds wintering in northern Europe, the effect of drier-than-normal conditions in the Mediterranean area during high NAO index winters is uncertain. The work presented here goes beyond simple correlative studies and help identifying which species that are most affected by variation in winter climate. This is a first important step that calls for a more mechanistic approach when analysing possible changes to climate change.
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| 5. |
- Norevik, Gabriel, et al.
(författare)
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Highly mobile insectivorous swifts perform multiple intra-tropical migrations to exploit an asynchronous African phenology
- 2019
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 128:5, s. 640-648
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Tidskriftsartikel (refereegranskat)abstract
- With timely allocated movement phases, mobile organisms can match their space-use with the seasonality of the environment and thereby optimise their resource utilisation over time. Long-distance avian migrants are known to move with the seasonal dynamics on an annual basis, but how individuals respond to seasonality within their tropical non-breeding range has been less studied. Here we analyse the movement pattern of a highly mobile aerial insectivorous bird, the pallid swift Apus pallidus, and its association with the local habitat phenology during the non-breeding period, using individual-based light-level geolocation. We extracted timing and location of 21 birds’ residence periods, as well as characteristics of the intervening movements, such as distance and speed. We used time series of precipitation and vegetation data for each residence area to extract the timing of the local end of the rainy season and the onset of the dry season. The pallid swifts repeatedly upgraded their habitat by undertaking 2–5 intra-tropical migrations correlated with the withdrawal of the rains and the onset of the local dry season. The birds arrived to the sites on average 12 days after rains ended and departed about two weeks after the onset of dry season suggesting that the birds closely tracked a spatiotemporal window presumably timed with optimal foraging conditions. Our results provide insights in the ways Palaearctic–African migrants respond to the asynchronous phenology within their sub-Saharan non-breeding range. We confirmed that pallid swifts actively respond to deteriorating conditions by repeated upgrades in habitat quality, which likely have substantial consequences for an individual's access to an essential, spatiotemporally ephemeral food resource. However, the pallid swifts did not surf an apparent resource wave per se as would be expected in a highly mobile species, indicating that also other factors, such as spatial patchiness of resources, may influence the movement decision.
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