Advanced

Seeking explanations for recent changes in abundance of wintering Eurasian Wigeon (Anas penelope) in northwest Europe

Fox, Anthony D.; Dalby, Lars; Christensen, Thomas Kjær; Nagy, Szabolcs; Balsby, Thorsten J S; Crowe, Olivia; Clausen, Preben; Deceuninck, Bernard; Devos, Koen and Holt, Chas A., et al. (2016) In Ornis Fennica 93(1). p.12-25
Abstract

We analysed annual changes in abundance of Eurasian Wigeon (Anas penelope) derived from mid-winter International Waterbird Census data throughout its northwest European flyway since 1988 using log-linear Poisson regression modelling. Increases in abundance in the north and east of the wintering range (Norway, Sweden, Denmark, Germany, Switzerland), stable numbers in the central range (Belgium, Netherlands, UK and France) and declining abundance in the west and south of the wintering range (Spain and Ireland) suggest a shift in wintering distribution consistent with milder winters throughout the range. However, because over 75% of the population of over 1 million individuals winters in Belgium, the Netherlands, UK and France, there was... (More)

We analysed annual changes in abundance of Eurasian Wigeon (Anas penelope) derived from mid-winter International Waterbird Census data throughout its northwest European flyway since 1988 using log-linear Poisson regression modelling. Increases in abundance in the north and east of the wintering range (Norway, Sweden, Denmark, Germany, Switzerland), stable numbers in the central range (Belgium, Netherlands, UK and France) and declining abundance in the west and south of the wintering range (Spain and Ireland) suggest a shift in wintering distribution consistent with milder winters throughout the range. However, because over 75% of the population of over 1 million individuals winters in Belgium, the Netherlands, UK and France, there was no evidence for a major movement in the centre of gravity of the wintering distribution. Between-winter changes in overall flyway abundance were highly significantly positively correlated (P = 0.003) with reproductive success measured by age ratios in Danish hunter wing surveys and less strongly and inversely correlated (P = 0.05) with mean January temperatures in the centre of the wintering range, suggesting that winter severity may also contribute to influence survival. However, adding winter severity to a model predicting population size based on annual reproductive success alone did not contribute to more effectively modelling the observed changes in population size. Patterns in annual reproductive success seem therefore to largely explain the recent dynamics in population size of northwest European Wigeon. Summer NAO significantly and positively explained 27% of variance in annual breeding success. Other local factors such as eutrophication of breeding sites and changes in predation pressure undoubtedly contribute to changes in the annual production of young and differences in hunting pressure as well as winter severity affect annual survival rates. However, it seems likely that the observed flyway population trend since 1988 has been mostly influenced by climate effects on the breeding grounds affecting reproductive success and marginally on the winter quarters affecting survival. We urge improved demographic monitoring of the population to better assess annual survival and reproductive success. We also recommend development of an adaptive management framework to remove uncertainties in our knowledge of Wigeon population dynamics as information is forthcoming to better inform management, especially to attempt to harmonise the harvest with annual changes in demography to ensure sustainable exploitation of this important quarry species now and in the future.

(Less)
Please use this url to cite or link to this publication:
author
, et al. (More)
(Less)
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Ornis Fennica
volume
93
issue
1
pages
14 pages
publisher
BirdLife Finland
external identifiers
  • scopus:84968909208
ISSN
0030-5685
language
English
LU publication?
yes
id
ac4724e9-cfab-447a-88e5-eae02aa85c93
date added to LUP
2017-02-07 11:05:38
date last changed
2017-10-01 05:30:00
@article{ac4724e9-cfab-447a-88e5-eae02aa85c93,
  abstract     = {<p>We analysed annual changes in abundance of Eurasian Wigeon (Anas penelope) derived from mid-winter International Waterbird Census data throughout its northwest European flyway since 1988 using log-linear Poisson regression modelling. Increases in abundance in the north and east of the wintering range (Norway, Sweden, Denmark, Germany, Switzerland), stable numbers in the central range (Belgium, Netherlands, UK and France) and declining abundance in the west and south of the wintering range (Spain and Ireland) suggest a shift in wintering distribution consistent with milder winters throughout the range. However, because over 75% of the population of over 1 million individuals winters in Belgium, the Netherlands, UK and France, there was no evidence for a major movement in the centre of gravity of the wintering distribution. Between-winter changes in overall flyway abundance were highly significantly positively correlated (P = 0.003) with reproductive success measured by age ratios in Danish hunter wing surveys and less strongly and inversely correlated (P = 0.05) with mean January temperatures in the centre of the wintering range, suggesting that winter severity may also contribute to influence survival. However, adding winter severity to a model predicting population size based on annual reproductive success alone did not contribute to more effectively modelling the observed changes in population size. Patterns in annual reproductive success seem therefore to largely explain the recent dynamics in population size of northwest European Wigeon. Summer NAO significantly and positively explained 27% of variance in annual breeding success. Other local factors such as eutrophication of breeding sites and changes in predation pressure undoubtedly contribute to changes in the annual production of young and differences in hunting pressure as well as winter severity affect annual survival rates. However, it seems likely that the observed flyway population trend since 1988 has been mostly influenced by climate effects on the breeding grounds affecting reproductive success and marginally on the winter quarters affecting survival. We urge improved demographic monitoring of the population to better assess annual survival and reproductive success. We also recommend development of an adaptive management framework to remove uncertainties in our knowledge of Wigeon population dynamics as information is forthcoming to better inform management, especially to attempt to harmonise the harvest with annual changes in demography to ensure sustainable exploitation of this important quarry species now and in the future.</p>},
  author       = {Fox, Anthony D. and Dalby, Lars and Christensen, Thomas Kjær and Nagy, Szabolcs and Balsby, Thorsten J S and Crowe, Olivia and Clausen, Preben and Deceuninck, Bernard and Devos, Koen and Holt, Chas A. and Hornman, Menno and Keller, Verena and Langendoen, Tom and Lehikoinen, Aleksi and Lorentsen, Svein Håkon and Molina, Blas and Nilsson, Leif and Stïpniece, Antra and Svenning, Jens-Christian and Wahl, Johannes},
  issn         = {0030-5685},
  language     = {eng},
  number       = {1},
  pages        = {12--25},
  publisher    = {BirdLife Finland},
  series       = {Ornis Fennica},
  title        = {Seeking explanations for recent changes in abundance of wintering Eurasian Wigeon (Anas penelope) in northwest Europe},
  volume       = {93},
  year         = {2016},
}