Survival patterns and density-dependent processes in breeding mallards Anas platyrhynchos
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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Högskolan Kristianstad, Institutionen för matematik och naturvetenskap
2007
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fthkristianstad:oai:DiVA.org:hkr-6782 2023-05-15T17:45:06+02:00 Survival patterns and density-dependent processes in breeding mallards Anas platyrhynchos Gunnarsson, Gunnar 2007 application/pdf http://urn.kb.se/resolve?urn=urn:nbn:se:hkr:diva-6782 eng eng Högskolan Kristianstad, Institutionen för matematik och naturvetenskap Umeå : Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences Acta Universitatis agriculturae Sueciae, 1652-6880 2007:12 http://urn.kb.se/resolve?urn=urn:nbn:se:hkr:diva-6782 urn:isbn:978-91-576-7311-4 info:eu-repo/semantics/openAccess broods dabbling ducks density dependence ducklings experiments models mortality nest predation regulation survival Ecology Ekologi Doctoral thesis, comprehensive summary info:eu-repo/semantics/doctoralThesis text 2007 fthkristianstad 2022-07-29T13:26:57Z 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 ... Doctoral or Postdoctoral Thesis Northern Sweden Kristianstad University College: Publications (DiVA) |
institution |
Open Polar |
collection |
Kristianstad University College: Publications (DiVA) |
op_collection_id |
fthkristianstad |
language |
English |
topic |
broods dabbling ducks density dependence ducklings experiments models mortality nest predation regulation survival Ecology Ekologi |
spellingShingle |
broods dabbling ducks density dependence ducklings experiments models mortality nest predation regulation survival Ecology Ekologi Gunnarsson, Gunnar Survival patterns and density-dependent processes in breeding mallards Anas platyrhynchos |
topic_facet |
broods dabbling ducks density dependence ducklings experiments models mortality nest predation regulation survival Ecology Ekologi |
description |
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 ... |
format |
Doctoral or Postdoctoral Thesis |
author |
Gunnarsson, Gunnar |
author_facet |
Gunnarsson, Gunnar |
author_sort |
Gunnarsson, Gunnar |
title |
Survival patterns and density-dependent processes in breeding mallards Anas platyrhynchos |
title_short |
Survival patterns and density-dependent processes in breeding mallards Anas platyrhynchos |
title_full |
Survival patterns and density-dependent processes in breeding mallards Anas platyrhynchos |
title_fullStr |
Survival patterns and density-dependent processes in breeding mallards Anas platyrhynchos |
title_full_unstemmed |
Survival patterns and density-dependent processes in breeding mallards Anas platyrhynchos |
title_sort |
survival patterns and density-dependent processes in breeding mallards anas platyrhynchos |
publisher |
Högskolan Kristianstad, Institutionen för matematik och naturvetenskap |
publishDate |
2007 |
url |
http://urn.kb.se/resolve?urn=urn:nbn:se:hkr:diva-6782 |
genre |
Northern Sweden |
genre_facet |
Northern Sweden |
op_relation |
Acta Universitatis agriculturae Sueciae, 1652-6880 2007:12 http://urn.kb.se/resolve?urn=urn:nbn:se:hkr:diva-6782 urn:isbn:978-91-576-7311-4 |
op_rights |
info:eu-repo/semantics/openAccess |
_version_ |
1766147866572619776 |