Age of first breeding in the Common Eider Somateria m. mollissima population in the northern Baltic Sea

The Baltic/Wadden Sea Common Eider (Somateria m. mollissima) population may have declined by one-third between 1991 and 2000, based on counts carried out on the species wintering grounds, Denmark in particular. However, less drastic reductions have been re-ported from the breeding grounds, mainly in...

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Main Authors: Hario, M., Rintala, J.
Format: Article in Journal/Newspaper
Language:English
Published: BirdLife Finland 2009
Subjects:
Online Access:https://ornisfennica.journal.fi/article/view/133724
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spelling fttsvojs:oai:journal.fi:article/133724 2023-09-05T13:18:52+02:00 Age of first breeding in the Common Eider Somateria m. mollissima population in the northern Baltic Sea Hario, M. Rintala, J. 2009-09-30 application/pdf https://ornisfennica.journal.fi/article/view/133724 eng eng BirdLife Finland https://ornisfennica.journal.fi/article/view/133724/82274 https://ornisfennica.journal.fi/article/view/133724 Ornis Fennica; Vol 86 Nro 3 (2009); 81–88 Ornis Fennica; Vol. 86 No. 3 (2009); 81–88 0030-5685 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Peer-reviewed Article 2009 fttsvojs 2023-08-23T23:03:04Z The Baltic/Wadden Sea Common Eider (Somateria m. mollissima) population may have declined by one-third between 1991 and 2000, based on counts carried out on the species wintering grounds, Denmark in particular. However, less drastic reductions have been re-ported from the breeding grounds, mainly in Finland and Estonia. It has been hypothe-sized that this discrepancy might arise from an earlier debut breeding attempt of subadult individuals. An increase in adult mortality may allow a larger proportion of subadult indi-viduals to start breeding and arrive to the breeding grounds at a younger age than before. Consequently, their numbers might mask the decline of the adult population. Accord-ingly, the decline of the entire population would then be discernable only on the joint win-tering grounds in the south, where all age classes occur together. Yet this study found no tendency towards earlier debut breeding in a declining Eider population in the Gulf of Finland. On the contrary, debut breeding was delayed as the population declined and the adult mortality increased. Later debut breeding and diminished population size were both related to poor fledging success three years earlier (i.e., the mean maturation age), which in turn was an outcome of mass mortality among ducklings. Debutants originating from small year classes (resulting from heavy duckling losses) took more time to become ma-ture and made a smaller contribution to the population growth rate than recruits of large year classes. Environmental conditions (e.g., food, pathogens) might affect the develop-ment of an individual, with late debutants having lower fitness than early debutants. The discrepancy between the size of the wintering stock and that of the breeding stock of Bal-tic/Wadden Sea Eiders might result from a decreasing fledging rate in the north and, to a lesser extent, from increased adult mortality. Article in Journal/Newspaper Common Eider Federation of Finnish Learned Societies: Scientific Journals Online
institution Open Polar
collection Federation of Finnish Learned Societies: Scientific Journals Online
op_collection_id fttsvojs
language English
description The Baltic/Wadden Sea Common Eider (Somateria m. mollissima) population may have declined by one-third between 1991 and 2000, based on counts carried out on the species wintering grounds, Denmark in particular. However, less drastic reductions have been re-ported from the breeding grounds, mainly in Finland and Estonia. It has been hypothe-sized that this discrepancy might arise from an earlier debut breeding attempt of subadult individuals. An increase in adult mortality may allow a larger proportion of subadult indi-viduals to start breeding and arrive to the breeding grounds at a younger age than before. Consequently, their numbers might mask the decline of the adult population. Accord-ingly, the decline of the entire population would then be discernable only on the joint win-tering grounds in the south, where all age classes occur together. Yet this study found no tendency towards earlier debut breeding in a declining Eider population in the Gulf of Finland. On the contrary, debut breeding was delayed as the population declined and the adult mortality increased. Later debut breeding and diminished population size were both related to poor fledging success three years earlier (i.e., the mean maturation age), which in turn was an outcome of mass mortality among ducklings. Debutants originating from small year classes (resulting from heavy duckling losses) took more time to become ma-ture and made a smaller contribution to the population growth rate than recruits of large year classes. Environmental conditions (e.g., food, pathogens) might affect the develop-ment of an individual, with late debutants having lower fitness than early debutants. The discrepancy between the size of the wintering stock and that of the breeding stock of Bal-tic/Wadden Sea Eiders might result from a decreasing fledging rate in the north and, to a lesser extent, from increased adult mortality.
format Article in Journal/Newspaper
author Hario, M.
Rintala, J.
spellingShingle Hario, M.
Rintala, J.
Age of first breeding in the Common Eider Somateria m. mollissima population in the northern Baltic Sea
author_facet Hario, M.
Rintala, J.
author_sort Hario, M.
title Age of first breeding in the Common Eider Somateria m. mollissima population in the northern Baltic Sea
title_short Age of first breeding in the Common Eider Somateria m. mollissima population in the northern Baltic Sea
title_full Age of first breeding in the Common Eider Somateria m. mollissima population in the northern Baltic Sea
title_fullStr Age of first breeding in the Common Eider Somateria m. mollissima population in the northern Baltic Sea
title_full_unstemmed Age of first breeding in the Common Eider Somateria m. mollissima population in the northern Baltic Sea
title_sort age of first breeding in the common eider somateria m. mollissima population in the northern baltic sea
publisher BirdLife Finland
publishDate 2009
url https://ornisfennica.journal.fi/article/view/133724
genre Common Eider
genre_facet Common Eider
op_source Ornis Fennica; Vol 86 Nro 3 (2009); 81–88
Ornis Fennica; Vol. 86 No. 3 (2009); 81–88
0030-5685
op_relation https://ornisfennica.journal.fi/article/view/133724/82274
https://ornisfennica.journal.fi/article/view/133724
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