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Survival patterns and density-dependent processes in breeding mallards Anas platyrhynchos

Gunnarsson, Gunnar (2007). Survival patterns and density-dependent processes in breeding mallards Anas platyrhynchos. Diss. (sammanfattning/summary) Umeå : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2007:12
ISBN 978-91-576-7311-4
[Doctoral thesis]

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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. However, survival rates were high, ranging from 0.66 to 0.81 for most groups (sex*age). The generality of density dependence was evident since such processes were detected in all studies. Consequently, depredation rate was higher in high nest density compared to low nest density. Survival of ducklings was density-dependent in both boreal and nemoral biotic regions, with food limitation being evident in the former region but not in the latter. In spite of their generality, density-dependent patterns varied within as well between years, and for nest predation rates also between landscape types. The findings about density dependence in breeding mallards in this thesis are novel since they are based on experiments. They are potentially of general interest for management because they embrace a variety of lakes in two geographically distant areas, each being representative for large temperate areas in the northern hemisphere. Detection of density dependence at the local scale may be important at larger scales, too, following the principle of ‘ideal preemptive distribution’ in a source-sink dynamic system.

Authors/Creators:Gunnarsson, Gunnar
Title:Survival patterns and density-dependent processes in breeding mallards Anas platyrhynchos
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :February 2007
Number of Pages:39
ALLI. Gunnarsson, G., Elmberg, J., Dessborn, L., Jonzén, N., Pöysä, H. & Valkama, J. Survival estimates, mortality patterns, and population growth of Fennoscandian mallards Anas platyrhynchos. (Manuscript). II. Pöysä, H., Elmberg, J., Gunnarsson, G., Nummi, P. & Sjöberg, K. 2004. Ecological basis of sustainable harvesting: is the prevailing paradigm of compensatory mortality still valid? Oikos 104, 612-615. III. Gunnarsson, G. & Elmberg, J. Density-dependent nest predation – an experiment with simulated mallard nests in contrasting landscapes. (Submitted manuscript). IV. Elmberg, J. & Gunnarsson, G. Are mallards ducking for predators? Local pair density affects nest survival differently in different landscapes. (Submitted manuscript). V. Gunnarsson, G., Elmberg, J., Sjöberg, K., Pöysä, H. & Nummi, P. 2006. Experimental evidence for density-dependent survival in mallard (Anas platyrhynchos) ducklings. Oecologia 149, 203-213. VI. Gunnarsson, G., Elmberg, J., Sjöberg, K., Pöysä, H. & Nummi, P. 2004. Why are there so many empty lakes? Food limits survival of mallard ducklings. Canadian journal of zoology 82, 1698-1703. VII. Elmberg, J., Gunnarsson, G., Pöysä, H., Sjöberg, K. & Nummi, P. 2005. Within-season sequential density dependence regulates breeding success in mallards Anas platyrhynchos. Oikos 108, 582-590.
Place of Publication:Umeå
ISBN for printed version:978-91-576-7311-4
Publication Type:Doctoral thesis
Full Text Status:Public
Agrovoc terms:ducks, population dynamics, survival, mortality, predation, nesting, sweden, finland
Keywords:broods, dabbling ducks, density dependence, ducklings, experiments, models, mortality, nest predation, regulation, survival
Permanent URL:
ID Code:1354
Department:(S) > Dept. of Wildlife, Fish and Environmental Studies
Deposited By: Gunnar Gunnarsson
Deposited On:28 Feb 2007 00:00
Metadata Last Modified:02 Dec 2014 10:11

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