Gunnar Gunnarsson
Measuring and assessing vital rates such as births and deaths are prerequisites for understanding population dynamics. Vital rates may be affected by the density of individuals, even though the importance of density dependence on population dynamics has been debated for a long time. The mallard Anas...
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| Format: | Text |
| Language: | English |
| Published: |
2007
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.631.3474 http://pub.epsilon.slu.se/1354/1/Kappa.pdf |
| Summary: | Measuring and assessing vital rates such as births and deaths are prerequisites for understanding population dynamics. Vital rates may be affected by the density of individuals, even though the importance of density dependence on population dynamics has been debated for a long time. The mallard Anas platyrhynchos is one of the foremost game species in the Holarctic, with millions of birds in hunters ’ bags annually. Still, basic knowledge about regulation of mallards ’ vital rates is poor, and experimental studies on this topic are rare. In this thesis I have studied survival patterns and density dependence in mallards breeding in Sweden and Finland. Long-term ringing data from both countries were analysed for mortality patterns and causation, as well as for e.g. survival rate estimation. Most of the studies were, though, experiments run over two years involving manipulations of the density of nests, broods and/or adults, in southern and northern Sweden, comprising different biotic regions. Common response variables were survival of nests, ducklings and hens, mainly analysed with program MARK. About 90 % of the recovered mallards in Finland and Sweden were hunting kills. |
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