| 1. |
- Frank, Jens, et al.
(författare)
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Åtgärder – minska viltskadorna
- 2010
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Ingår i: Vilt, människa, samhälle. - 9789147094189 ; , s. 285-301
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Bokkapitel (populärvet., debatt m.m.)
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| 2. |
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| 3. |
- Helldin, Jan Olof, et al.
(författare)
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Viltet i samhället
- 2010
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Ingår i: Vilt, människa, samhälle. - 9789147094189 ; , s. 135-168
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Bokkapitel (populärvet., debatt m.m.)
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| 4. |
- Klaassen, Raymond, et al.
(författare)
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Geographical and temporal flexibility in the response to crosswinds by migrating raptors.
- 2011
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Ingår i: Proceedings of the Royal Society B: Biological Sciences. - : The Royal Society. - 1471-2954 .- 0962-8452. ; 278, s. 1339-1346
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Tidskriftsartikel (refereegranskat)abstract
- Wind and ocean currents may potentially have important effects on travelling animals, as an animal which does not respond to lateral flow will be drifted from its intended direction of movement. By analysing daily movements of migrating ospreys Pandion haliaetus and marsh harriers Circus aeruginosus, as recorded by satellite telemetry, in relation to global wind data, we showed that these raptors allow on average 47 per cent drift. Furthermore, our analyses revealed significant geographical and temporal variation in the response to crosswinds. During some parts of the migration, the birds drifted and in other parts they compensated or even overcompensated. In some regions, the response of marsh harriers depended on the wind direction. They drifted when the wind came from one side and (over)compensated when the wind came from the opposite side, and this flexible response was different in different geographical regions. These results suggest that migrating raptors modulate their response to crosswinds at different places and times during their travels and show that individual birds use a much more varied repertoire of behavioural responses to wind than hitherto assumed. Our results may also explain why contrasting and variable results have been obtained in previous studies of the effect of wind on bird migration.
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| 5. |
- Klaassen, Raymond, et al.
(författare)
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Loop migration in adult marsh harriers Circus aeruginosus, as revealed by satellite telemetry
- 2010
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Ingår i: Journal of Avian Biology. - 0908-8857 .- 1600-048X. ; 41:2, s. 200-207
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Tidskriftsartikel (refereegranskat)abstract
- Loop migration among birds is characterized by the spring route lying consistently west or east of the autumn route. The existence of loops has been explained by general wind conditions or seasonal differences in habitat distribution. Loop migration has predominantly been studied at the population level, for example by analysing ring recoveries. Here we study loop migration of individual marsh harriers Circus aeruginosus tracked by satellite telemetry. We show that despite a generally narrow migration corridor the harriers travelled in a distinct clockwise loop through Africa and southern Europe, following more westerly routes in spring than in autumn. We used the Normalized Difference Vegetation Index (NDVI) to identify potential feeding habitat in Africa. Suitable habitat seemed always more abundant along the western route, both in spring and autumn, and no important stopover site was found along the eastern route. Observed routes did thus not coincide with seasonal variation in habitat availability. However, favourable habitat might be more important during spring migration, when the crossing of the Sahara seems more challenging, and thus habitat availability might play an indirect role in the harriers' route choice. Grid-based wind data were used to reconstruct general wind patterns, and in qualitative agreement with the observed loop marsh harriers predominantly encountered westerly winds in Europe and easterly winds in Africa, both in autumn and in spring. By correlating tail- and crosswinds with forward and perpendicular movement rates, respectively, we show that marsh harriers are partially drifted by wind. Thus, we tentatively conclude that wind rather than habitat seems to have an overriding effect on the shape of the migration routes of marsh harriers. General wind conditions seem to play an important role also in the evolution of narrow migratory loops as demonstrated for individual marsh harriers.
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| 6. |
- Klaassen, Raymond, et al.
(författare)
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When and where does mortality occur in migratory birds? Direct evidence from long-term satellite tracking of raptors.
- 2014
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Ingår i: Journal of Animal Ecology. - : Wiley. - 1365-2656 .- 0021-8790. ; 83:1, s. 176-184
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Tidskriftsartikel (refereegranskat)abstract
- Information about when and where animals die is important to understand population regulation. In migratory animals, mortality might occur not only during the stationary periods (e.g. breeding and wintering) but also during the migration seasons. However, the relative importance of population limiting factors during different periods of the year remains poorly understood, and previous studies mainly relied on indirect evidence. Here, we provide direct evidence about when and where migrants die by identifying cases of confirmed and probable deaths in three species of long-distance migratory raptors tracked by satellite telemetry. We show that mortality rate was about six times higher during migration seasons than during stationary periods. However, total mortality was surprisingly similar between periods, which can be explained by the fact that risky migration periods are shorter than safer stationary periods. Nevertheless, more than half of the annual mortality occurred during migration. We also found spatiotemporal patterns in mortality: spring mortality occurred mainly in Africa in association with the crossing of the Sahara desert, while most mortality during autumn took place in Europe. Our results strongly suggest that events during the migration seasons have an important impact on the population dynamics of long-distance migrants. We speculate that mortality during spring migration may account for short-term annual variation in survival and population sizes, while mortality during autumn migration may be more important for long-term population regulation (through density-dependent effects).
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| 7. |
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| 9. |
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| 10. |
- Månsson, Johan, et al.
(författare)
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Territory size and habitat selection of breeding Common Cranes (Grus grus) in a boreal landscape
- 2013
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Ingår i: Ornis Fennica. - 0030-5685. ; 90, s. 65-72
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Tidskriftsartikel (refereegranskat)abstract
- Information on how birds use different types of habitat and move within landscapes is crucial for avian ecology, conservation and management. The Common Crane Grus grus has the widest distribution of all crane species and covers both increasing and decreasing populations. Ecological knowledge is therefore necessary both for conservation and to mitigate bird-human conflicts. We studied territory size and habitat selection of breeding Common Cranes (n=11) at two spatial scales in south-central Sweden by using VHF and UPS transmitters. Breeding families of Cranes were strongly associated with farmlands and wetlands independent of spatial scale. However, 41% of positions were within forested habitats. According to a compositional analysis, moist and wet forests were selected more frequently than dry forests. Territory size was on average 250 ha +/- 47.8 SE. The territories showed little overlap between neighboring breeding pairs. Our study provides information necessary for estimating densities of breeding pairs, but also to indicate habitat types worth special attention by landscape managers and conservationists.
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