| 1. |
- Chapman, Ben, et al.
(författare)
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Partial migration: an introduction
- 2011
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 120:12, s. 1761-1763
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Chapman, Ben, et al.
(författare)
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The ecology and evolution of partial migration
- 2011
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 120:12, s. 1764-1775
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Tidskriftsartikel (refereegranskat)abstract
- Partial migration, where populations of animals are composed of a mixture of resident and migratory individuals, is a widespread phenomenon in nature. It has been reported to occur in all major vertebrate groups, and can have significant ecological consequences. Here we give an overview of the ecology and evolution of partial migration in animals. We firstly review the different types of partial migration, and assess the ecological drivers responsible for driving individual differences in migratory tendency within populations. A variety of factors can be important in promoting the evolution of partial migration, including competition for resources or breeding opportunities, predation risk and intraspecific niche diversity. Often various factors act synergistically to create complex patterns of movement polymorphism within populations. The question of how partial migration is maintained over evolutionary timescales is also addressed. Whilst many theoretical considerations of partial migration utilise an evolutionary stable state (ESS) paradigm, empirical evidence for this is lacking. Rather the evidence suggests that partial migration is mostly condition dependent, and the optimum outcome for an individual is dependent upon its phenotype. What determines whether an individual follows a migratory or resident strategy is discussed in light of new theory and empirical data which supports the idea that environmentally responsive genetic thresholds are important across a range of species, from birds to fish, in proximately shaping migratory tendency. Finally we espouse our vision of how partial migration research will develop in the future, and suggest a number of exciting directions that studies into migratory dimorphism may take in the coming years.
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| 3. |
- Molokwu, Mary Ngozi, et al.
(författare)
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Seasonal variation in patch use in a tropical African environment
- 2008
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 117:6, s. 892-898
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Tidskriftsartikel (refereegranskat)abstract
- We used giving-up densities (GUD) to study patch use decisions of small granivorous passerines throughout the year. We measured GUDs continuously in four sites for a period of 9-10 months per year during 2004 and 2005 in a savannah area in Jos, central Nigeria. The study thus covered a period from the middle of the dry season, through the wet season to the beginning of the next dry season in each year. We placed experimental food patches in both open areas and in cover to investigate possible effects of predation risk and thermal hazard on the foraging behavior of the birds. We found a difference in GUDs between the microhabitats, with a consistently lower GUD in cover throughout the year and for the two years. During both years GUDs followed a pattern coinciding with the seasonal change in local seed availability. An initial decline in GUDs late in the dry season was followed by a steady increase during and after the rains. A similar trend in GUDs observed for both years supports the conclusion that GUDs measure the feeding birds' assessment of environmental quality, possibly in combination with other factors changing predictably during the year. We conclude that food abundance may act with other environmental and ecological factors to affect foraging decisions throughout the year.
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| 4. |
- Nilsson, Anna, et al.
(författare)
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Basal metabolic rate and energetic cost of thermoregulation among migratory and resident blue tits
- 2011
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 120:12, s. 1784-1789
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Tidskriftsartikel (refereegranskat)abstract
- Metabolic rates may be informative of adaptations to migration or wintering at high latitudes and may therefore be particularly interesting in partial migrants requiring adaptations to both migration and residency. To study the extent of physiological adaptations in migratory and resident blue tits Cyanistes caeruleus during the period of autumn migration in southern Sweden, we measured basal metabolic rate (BMR) and cost of thermoregulation at 0 degrees C (CTR0). In contrast to other migrants en route, migratory blue tits had lower BMR than residents. As migratory blue tits travel extraordinarily slowly on autumn migration and residents suffer from harsher climate and severe competition, residents may need dynamic adjustments that involve larger metabolic costs than migrants. Resident males had lower CTR0 than migrants and resident females. Resident males are socially dominant, which suggests that they have priority of access to food sources during summer and early autumn. They also spend more time on moult, which would give them the time and energy needed for molting into a plumage of higher insulation quality than is possible for migrants and resident females.
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| 5. |
- Nilsson, Jan-Åke, et al.
(författare)
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Postnatal effects of incubation length in mallard and pheasant chicks
- 2004
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 105:3, s. 588-594
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Tidskriftsartikel (refereegranskat)abstract
- Eggs of mallard ducks (Anas platyrhynchos) and ring-necked pheasants (Phasianus colchicus) were incubated in clutches arranged to stimulate embryos to hatch earlier or later than normal. This manipulation of hatching time was achieved by combining eggs of different age in the same clutch. To ensure hatching synchrony, embryos communicate with each other during the last stage of incubation, resulting in either a delay or an acceleration of hatching. Embryos of both species that accelerated their hatching time suffered a higher mortality rate after hatching. Combining mortality with the proportion of hatchlings that suffered from leg deformities, impeding their movements, resulted in a cost also to pheasant chicks delaying their hatching. Chicks of both species accelerating hatching time had a lower minimum mass and a shorter tarsus length than control chicks, whereas chicks delaying hatching time either grew as well or slightly better than control chicks. Mallard chicks had better balance and mobility immediately after hatching the longer they stayed in the egg. This indicates that the period immediately before hatching, is an important period for muscular and organ maturity. Reducing this period results in costs affecting post-hatching survival. The strategy to assure synchronous hatching in mallards and pheasants probably reflect a trade-off between the negative effects of shifting the age at hatching away from normal and differences in predation risk during different stages of reproduction.
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| 6. |
- Nilsson, Jan-Åke
(författare)
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Time-dependent reproductive decisions in the blue tit
- 2000
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 88:2, s. 351-361
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Tidskriftsartikel (refereegranskat)abstract
- Many breeding attempts in birds do not result in any fledged young due to predation on eggs or young. Consequently, the influence of time constraints on reproductive decisions are integrated parts of the reproductive behaviour of birds breeding within short, seasonal climate zones. In this study. I mimicked nest predation by removing blue tit (Parus caeruleus) clutches shortly after completion. Around 75% of the removed clutches were followed by a repeat clutch. Females producing their first clutch early in the season and females with an early onset of incubation in the laying sequence (an indication of high parental or territory quality) were most likely to initiate a repeat clutch. A trade-off between the benefits of a repeat clutch and survival likely stopped late Females in bad condition from investing more in the current reproductive season. Females producing a repeat clutch laid fewer eggs, had an earlier onset of incubation in the laying sequence and produced larger eggs than they did when producing their original first clutch. Eggs produced after the onset of incubation were especially large in the repeat clutches. Since food availability was presumably higher when the female produced her repeat clutch compared with her first clutch, females made a strategical decision when reducing clutch size, whereas onset of incubation and egg size may have been energetically constrained when producing the first clutch. Females that produced a relatively large clutch, had a relatively early onset of incubation, and laid relatively large eggs in their first clutch also did so when producing a repeat clutch, indicating that some of the variation in breeding parameters are due to differences in parental or territory quality. Differences between years in the temperature-dependent development rate of caterpillars seem to affect the time constraints on breeding. A year with a predicted early seasonal decline in caterpillars resulted in short intervals between removal and relaying, small clutches and an early onset of incubation.
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| 7. |
- Ellis, Vincenzo A., et al.
(författare)
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Explaining prevalence, diversity and host specificity in a community of avian haemosporidian parasites
- 2020
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 129:9, s. 1314-1329
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Tidskriftsartikel (refereegranskat)abstract
- Many hypotheses attempt to explain parasite–host associations, but rarely are they examined together in a single community. For hosts, key traits are the proportion of infected individuals (prevalence) and the diversity of parasites infecting them. A key parasite trait is host specificity, ranging from specialists infecting one or a few closely related species to generalists infecting many species. We tested 10 hypotheses to explain host-parasite associations; five ‘host-centric’ (e.g. prevalence is related to host abundance) and five ‘parasite-centric’ (e.g. parasite abundance is related to host specificity). We analyzed a community of 67 locally transmitted avian haemosporidian parasite lineages (genera Plasmodium, Haemoproteus or Leucocytozoon), sampled from 2726 birds (64 species) in southern Sweden. Among host-centric hypotheses, Haemoproteus and Leucocytozoon prevalence and Haemoproteus diversity were related to host habitat preferences, whereas there were no relationships with host abundance or body mass. Haemoproteus and Leucocytozoon prevalences were more similar among closely related than among distantly related host species. Haemoproteus prevalence and diversity were lower in host species with few close relatives (‘evolutionarily distinct’ hosts). Among parasite-centric hypotheses, most lineages, even relative generalists, infected closely related host species more often than expected by chance. However, the host species of Haemoproteus and Leucocytozoon lineages overlapped less among lineages than expected by chance. Specialists did not reach higher prevalences than generalists on single host species. However, the abundance of Haemoproteus lineages was related to host specificity with generalists more common than specialists; this was driven by three closely related generalists. Host specificity of parasites was unrelated to the abundance or evolutionarily distinctiveness of their hosts. Parasite communities are likely structured by many factors and cannot be explained by hypotheses focusing solely on hosts or parasites. However, we found consistent effects of host phylogenetic relationships, plausibly a result of evolutionarily conserved host immune systems limiting parasite distributions.
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| 8. |
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| 9. |
- Johansson, Jacob, et al.
(författare)
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The eco-evolutionary consequences of interspecific phenological asynchrony - a theoretical perspective
- 2015
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 124:1, s. 102-112
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Forskningsöversikt (refereegranskat)abstract
- The timing of biological events (phenology) is an important aspect of both a species' life cycle and how it interacts with other species and its environment. Patterns of phenological change have been given much scientific attention, particularly recently in relation to climate change. For pairs of interacting species, if their rates of phenological change differ, then this may lead to asynchrony between them and disruption of their ecological interactions. However it is often difficult to interpret differential rates of phenological change and to predict their ecological and evolutionary consequences. We review theoretical results regarding this topic, with special emphasis on those arising from life history theory, evolutionary game theory and population dynamic models. Much ecological research on phenological change builds upon the concept of match/mismatch, so we start by putting forward a simple but general model that captures essential elements of this concept. We then systematically compare the predictions of this baseline model with expectations from theory in which additional ecological mechanisms and features of species life cycles are taken into account. We discuss the ways in which the fitness consequences of interspecific phenological asynchrony may be weak, strong, or idiosyncratic. We discuss theory showing that synchrony is not necessarily an expected evolutionary outcome, and how population densities are not necessarily maximized by adaptation, and the implications of these findings. By bringing together theoretical developments regarding the eco-evolutionary consequences of phenological asynchrony, we provide an overview of available alternative hypotheses for interpreting empirical patterns as well as the starting point for the next generation of theory in this field.
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| 10. |
- Nord, Andreas, et al.
(författare)
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A trade-off between perceived predation risk and energy conservation revealed by an immune challenge experiment
- 2014
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 123:9, s. 1091-1100
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Tidskriftsartikel (refereegranskat)abstract
- Energy is typically a limiting factor for animals during boreal zone winters, when low temperatures increase the cost of thermoregulation at the same times as short day-lengths and snow cover constrain foraging opportunities. Under these circumstances animals use a suite of behavioural and physiological adaptations to avoid overnight starvation. However, it is poorly understood how such strategies are affected by increased energy demands from other physiological systems. Thus, we used free-ranging blue tits (Cyanistes caeruleus L.) to test if competing demands for energy (here induced by a non-inflammatory, antibody-mediated immune challenge) would affect nocturnal body temperature (a predictor of energy expenditure in small animals) and energy-saving nest box roosting behaviour. We also assessed if the immune challenge incurred long-term survival costs. We found no evidence that body temperature regulation differed between immune-challenged and saline-injected birds. Nor did the immune challenge reduce survival to the next breeding season. However, old (second winter or older) immune-challenged birds continued roosting in nest boxes to a larger extent at the peak immune response, despite increased perceived predation risk induced by the preceding capture and immunization. In contrast, old control birds were less prone to roost in nest boxes after capture and saline injection. This difference was less pronounced in young (first winter) birds. We interpret the increased risk-taking behaviour in immune-challenged birds as a consequence of a higher need for exploiting the thermal benefits of nest box roosting to reduce energy loss. This suggests that resource deficiency might be a stronger predictor of overnight survival than the threat of nocturnal predation in this system. As such, our study provides insights into the classic trade-off between starvation and predation risk, in suggesting that priority is given to minimizing the risk of starvation in situations where both starvation and predation risks increase during cold winter nights.
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