| 1. |
- Low, Matthew, et al.
(författare)
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Habitat-specific differences in adult survival rates and its links to parental workload and on-nest predation
- 2010
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Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 79, s. 214-224
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Tidskriftsartikel (refereegranskat)abstract
- P>1. Adult survival rates strongly affect population growth, but few studies have quantified if and why adult survival differs between breeding habitats. We investigated potential causes of habitat-specific adult survival rates for male and female northern wheatears (Oenanthe oenanthe L.) breeding in Swedish farmland.2. We used multistate mark-recapture models based on 1263 breeding records between 1993 and 2007 to estimate survival rates based on habitat-type (SHORT vs. TALL ground vegetation) and breeding-success state parameters. We also used breeding-season observations from 2002 to 2007 and an experimental manipulation of ground vegetation height to identify factors influencing adult mortality.3. Females had lower annual survival than males (0 center dot 42 +/- 0 center dot 02 vs. 0 center dot 50 +/- 0 center dot 02); this difference largely resulted from low female survival in TALL habitats because of higher nest-predation risk and the large proportion of adult females being killed on the nest (> 20%) during nest predation events.4. Among successful breeders, both sexes displayed similar survival rates, but survival was lower for breeders in TALL as compared to SHORT habitats (0 center dot 43 +/- 0 center dot 03 vs. 0 center dot 51 +/- 0 center dot 02). Experimental manipulation of ground vegetation height, controlling for individual and territory quality (n = 132), suggested the cost of rearing young to be higher in TALL habitats (survival of successful breeders in TALL vs. SHORT; 0 center dot 43 +/- 0 center dot 11 vs. 0 center dot 57 +/- 0 center dot 05).5. Detailed observations of food provisioning behaviour during chick rearing revealed a habitat-related difference in parental workload corresponding to the observed habitat differences in adult survival for successful breeders. Adults breeding in TALL habitats were forced to forage further from the nest relative to SHORT-habitat breeders (mean +/- SE; 69 +/- 10 vs. 21 +/- 2 m), which increased the estimated daily workload for adults in TALL vs. SHORT habitats by c. 20%.6. On-nest predation and parental workload during chick rearing combine to largely explain habitat-specific adult survival rates. The results have implications for our understanding of adult sex ratios, causes of source-sink demography and habitat-specific growth rates. Furthermore, it suggests SHORT field margins and other residual habitat elements to be important for the conservation of farmland passerines breeding in cropland plains.
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| 2. |
- Nystrand, Magdalena, et al.
(författare)
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Habitat-specific demography and source-sink dynamics in a population of Siberian jays
- 2010
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Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 79:1, s. 266-274
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Tidskriftsartikel (refereegranskat)abstract
- There are a number of models describing population structure, many of which have the capacity to incorporate spatial habitat effects. One such model is the source-sink model, that describes a system where some habitats have a natality that is higher than mortality (source) and others have a mortality that exceeds natality (sink). A source can be maintained in the absence of migration, whereas a sink will go extinct. 2. However, the interaction between population dynamics and habitat quality is complex, and concerns have been raised about the validity of published empirical studies addressing source-sink dynamics. In particular, some of these studies fail to provide data on survival, a significant component in disentangling a sink from a low quality source. Moreover, failing to account for a density-dependent increase in mortality, or decrease in fecundity, can result in a territory being falsely assigned as a sink, when in fact, this density-dependent suppression only decreases the population size to a lower level, hence indicating a 'pseudo-sink'. 3. In this study, we investigate a long-term data set for key components of territory-specific demography (mortality and reproduction) and their relationship to habitat characteristics in the territorial, group-living Siberian jay (Perisoreus infaustus). We also assess territory-specific population growth rates (r), to test whether spatial population dynamics are consistent with the ideas of source-sink dynamics. 4. Although average mortality did not differ between sexes, habitat-specific mortality did. Female mortality was higher in older forests, a pattern not observed in males. Male mortality only increased with an increasing amount of open areas. Moreover, reproductive success was higher further away from human settlement, indicating a strong effect of human-associated nest predators. 5. Averaged over all years, 76% of the territories were sources. These territories generally consisted of less open areas, and were located further away from human settlement. 6. The source-sink model provides a tool for modelling demography in distinct habitat patches of different quality, which can aid in identifying key habitats within the landscape, and thus, reduce the risk of implementing unsound management decisions.
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| 3. |
- Kindberg, Jonas
(författare)
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Male reproductive strategy explains spatiotemporal segregation in brown bears
- 2013
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Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 82, s. 836-845
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Tidskriftsartikel (refereegranskat)abstract
- Spatiotemporal segregation is often explained by the risk for offspring predation or by differences in physiology, predation risk vulnerability or competitive abilities related to size dimorphism. Most large carnivores are size dimorphic and offspring predation is often intraspecific and related to nonparental infanticide (NPI). NPI can be a foraging strategy, a strategy to reduce competition, or a male reproductive strategy. Spatiotemporal segregation is widespread among large carnivores, but its nature remains poorly understood. We evaluated three hypotheses to explain spatiotemporal segregation in the brown bear, a size-dimorphic large carnivore in which NPI is common; the NPI - foraging/competition hypothesis', i.e. NPI as a foraging strategy or a strategy to reduce competition, the NPI - sexual selection hypothesis', i.e. infanticide as a male reproductive strategy and the body size hypothesis', i.e. body-size-related differences in physiology, predation risk vulnerability or competitive ability causes spatiotemporal segregation. To test these hypotheses, we quantified spatiotemporal segregation among adult males, lone adult females and females with cubs-of-the-year, based on GPS-relocation data (2006-2010) and resource selection functions in a Scandinavian population. We found that spatiotemporal segregation was strongest between females with cubs-of-the-year and adult males during the mating season. During the mating season, females with cubs-of-the-year selected their resources, in contrast to adult males, in less rugged landscapes in relative close proximity to certain human-related variables, and in more open habitat types. After the mating season, females with cubs-of-the-year markedly shifted their resource selection towards a pattern more similar to that of their conspecifics. No strong spatiotemporal segregation was apparent between females with cubs-of-the-year and conspecifics during the mating and the postmating season. The NPI - sexual selection hypothesis' best explained spatiotemporal segregation in our study system. We suggest that females with cubs-of-the-year alter their resource selection to avoid infanticidal males. In species exhibiting NPI as a male reproductive strategy, female avoidance of infanticidal males is probably more common than observed or reported, and may come with a fitness cost if females trade safety for optimal resources.
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| 4. |
- Kindberg, Jonas
(författare)
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Sociodemographic factors modulate the spatial response of brown bears to vacancies created by hunting
- 2018
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Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 87, s. 247-258
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Tidskriftsartikel (refereegranskat)abstract
- 1. There is a growing recognition of the importance of indirect effects from hunting on wildlife populations, e.g. social and behavioural changes due to harvest, which occur after the initial offtake. Nonetheless, little is known about how the removal of members of a population influences the spatial configuration of the survivors.2. We studied how surviving brown bears (Ursus arctos) used former home ranges that had belonged to casualties of the annual bear hunting season in southcentral Sweden (2007-2015). We used resource selection functions to explore the effects of the casualty's and survivor's sex, age and their pairwise genetic relatedness, population density and hunting intensity on survivors' spatial responses to vacated home ranges.3. We tested the competitive release hypothesis, whereby survivors that increase their use of a killed bear's home range are presumed to have been released from intraspecific competition. We found strong support for this hypothesis, as survivors of the same sex as the casualty consistently increased their use of its vacant home range. Patterns were less pronounced or absent when the survivor and casualty were of opposite sex.4. Genetic relatedness between the survivor and the casualty emerged as the most important factor explaining increased use of vacated male home ranges by males, with a stronger response from survivors of lower relatedness. Relatedness was also important for females, but it did not influence use following removal; female survivors used home ranges of higher related female casualties more, both before and after death. Spatial responses by survivors were further influenced by bear age, population density and hunting intensity.5. We have shown that survivors exhibit a spatial response to vacated home ranges caused by hunting casualties, even in nonterritorial species such as the brown bear. This spatial reorganization can have unintended consequences for population dynamics and interfere with management goals. Altogether, our results underscore the need to better understand the short- and long-term indirect effects of hunting on animal social structure and their resulting distribution in space.
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| 5. |
- Emery, Sara, et al.
(författare)
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Cold winters drive consistent and spatially synchronous 8-year population cycles of cabbage stem flea beetle
- 2022
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Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 92, s. 594-605
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Tidskriftsartikel (refereegranskat)abstract
- 1. Population cycles have been observed in mammals as well as insects, but consistent population cycling has rarely been documented in agroecosystems and never for a beetle.2. We analysed the long term population patterns of the cabbage stem flea beetle Psylliodes chrysocephala in winter oilseed rape over 50 years.3. Psylliodes chrysocephala larval density from 3045 winter oilseed rape fields in southern Sweden showed strong 8 year population cycles in regional mean density. Fluctuations in larval density were synchronous over time across five subregional populations. Subregional mean environmental variables explained 90.6% of the synchrony in P. chrysocephala populations at the 7-11 year time-scale. The number of days below -10 degrees C showed strong anti phase coherence with larval densities in the 7-11 year time-scale, such that more cold days resulted in low larval densities. High levels of the North Atlantic Oscillation weather system are coherent and anti phase with cold weather in Scania, Sweden.4. At the field-scale, later crop planting date and more cold winter days were associated with decreased overwintering larval density. Warmer autumn temperatures, resulting in greater larval accumulated degree days early in the season, increased overwintering larval density.5. Despite variation in environmental conditions and crop management, 8 year cycles persisted for cabbage stem flea beetle throughout the 50 years of data collection. Moran effects, influenced by the North Atlantic Oscillation weather patterns, are the primary drivers of this cycle and synchronicity. Insect pest data collected in commercial agriculture fields is an abundant source of long term data. We show that an agricultural pest can have the same periodic population cycles observed in perennial and unmanaged ecosystems. This unexpected find- ing has implications for sustainable pest management in agriculture and shows the value of long term pest monitoring projects as an additional source of time series data to untangle the drivers of population cycles.
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| 6. |
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| 7. |
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| 8. |
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| 9. |
- Low, Matthew, et al.
(författare)
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Patterns of mortality for each life-history stage in a population of the endangered New Zealand stitchbird
- 2009
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Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 78, s. 761-771
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Tidskriftsartikel (refereegranskat)abstract
- Using data from 396 breeding attempts over an 8-year period, we investigated age- and stage-specific survival rates and their modifying factors in a closed island population of the New Zealand stitchbird (or hihi, Notiomystis cincta Du Bus).Survival probability generally increased over time; however, at each life-history transition, survival in the new stage started lower than at the end of the previous stage, creating a 'saw-tooth' function of age-related survival.The probability of an egg hatching was low (0.73 +/- 0.01): most likely a consequence of genetic bottlenecks previously endured by this population. There was strong support for a positive relationship between hatching rate and the subsequent survival of the female parent, and hatching success declining for females > 4 years old.Nestling survival probability increased as a function of brood size and days since hatching, and decreased relative to daily maximum ambient temperature and hatching date. Support for models including ambient temperature was greater than for other covariates, with the majority of this temperature-mediated survival effect being restricted to the early nestling stage.Fledglings had low survival rates in the first two weeks after leaving the nest, with post-fledging survival related to the fledgling's mass. Two months after fledging, juvenile survival probability plateaued and remained relatively constant for the following autumn, winter and spring/summer breeding season. There was no effect of sex or season on adult survival probability. However, there was strong support for age-specific variation in adult survival, with survival likelihood increasing during the first four years before showing evidence of a senescence decline.Within-stage survival increases were likely related to stage-specific selection pressures initially weeding out individuals of poorer phenotypes for the environment specific to each life-history stage. Such a mechanism explains the initial high mortality at life-history transitions; a well-adapted phenotype for one stage may not necessarily be so well adapted for subsequent stages. These patterns are not only valuable for examining life-history theory, but also for understanding the regulation of vital rates in an endangered species and providing a basis from which better population management models and harvesting regimes can be derived.
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| 10. |
- Schroeder, Martin
(författare)
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Long-term priority effects among insects and fungi colonizing decaying wood
- 2011
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Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 80, s. 1155-1162
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Tidskriftsartikel (refereegranskat)abstract
- 5. The study shows that variable priority effects may have long-lasting impact on community assembly in decaying wood. The study also exemplifies new possibilities for managing populations of threatened species by exploring links between early, well-understood species guilds and late, more poorly understood species guilds.
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