Could falling female sex ratios among first‐winter northwest European duck populations contribute to skewed adult sex ratios and overall population declines?

Fox, Anthony D.; Cristensen, Thomas K.

doi:10.1111/ibi.12649

Cited by 6 publications

(17 citation statements)

References 37 publications

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“…Our results contradict those of Christensen and Fox (2014) who found that the proportion of adult females among samples of hunter-shot birds from Denmark increased for the Tufted Duck (see also Fox and Christensen 2018) and decreased, although not significantly, for the Common Pochard in 1982-2010. Brides et al (2017) also found that the proportion of Common Pochard females in the International Waterbird Census, done in mid-winter in Europe and North Africa, decreased from 1989-1990 to 2016.…”

Section: Discussioncontrasting

confidence: 99%

“…Brides et al 2017). A similar link has been suggested for changes in sex ratios and population declines in many other duck species in Europe (Fox and Christensen 2018). A male-biased sex ratio per se may not affect population growth rate and dynamics because, given the surplus of males, female reproduction should not be limited by male availability.…”

Section: Discussionsupporting

confidence: 62%

“…These contradictory findings from breeding and wintering areas are difficult to explain, given the paucity of research on factors affecting variation in sex ratios in these and other duck species. Fox and Christensen (2018) discussed potential problems associated with measuring sex ratios from hunter-shot birds, and Brides et al (2017) discussed corresponding problems with mid-winter waterbird counts. In general, concerning data from wintering areas, be it hunter-shot birds or field counts, sex and between-year differences in migration, wintering areas and weather-induced movements, coupled with climate change-driven long-term changes in these (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…While variation of sex ratios of European ducks during the non-breeding season has been studied extensively (e.g. Nilsson 1970;Owen and Dix 1986;Carbone and Owen 1995;Brides et al 2017;Fox and Christensen 2018), research on sex ratio variation among breeding ducks is limited. Because staging and wintering areas gather birds from different parts of the breeding range, and the origin of birds usually remains unknown, data from wintering areas are not well suited to the study of specific mechanisms behind changes in sex ratios.…”

Section: Introductionmentioning

confidence: 99%

“…Samples of hunter-shot birds from Denmark indicate that the proportion of females amongst adult Tufted Ducks increased from 1982 to 2017 (Fox and Christensen 2018) but not in the Common Pochard from 1982 to 2010 (Christensen and Fox 2014). Adult sex ratios among the hunter-shot birds from Denmark also indicate considerable between-year variation for both species (see Christensen and Fox 2014;Fox and Christensen 2018) but factors affecting the variation have not been studied. As recently found in the Common Eider and Mandarin Duck (see above), lower survival of females during the breeding season may contribute to male-biased sex ratios, this being one of the earliest hypotheses put forward to explain malebiased sex ratios in waterfowl (Bellrose et al 1961).…”

Section: Introductionmentioning

confidence: 99%

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Breeding sex ratios in two declining diving duck species: between-year variation and changes over six decades

Pöysä

Linkola²,

Paasivaara

2019

J Ornithol

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Sex ratio variation has important consequences for population dynamics and viability. Adult sex ratio is male biased in many duck species, and data from wintering areas suggest male bias has been increasing in some European duck species. However, the reasons for changes in sex ratios remain poorly understood, and information on sex ratio variation among breeding ducks is limited. We studied long-term changes in breeding sex ratios and breeding numbers in Common Pochard Aythya ferina and Tufted Duck Aythya fuligula in southern Finland, the former species being currently assessed as critically endangered and the latter as endangered in Finland. In addition, we tested the hypothesis that between-year variation in breeding sex ratios is affected by the severity of weather conditions in the wintering areas. The proportion of females among breeding Tufted Ducks decreased from 42.9% in 1951-1970 to 36.9% in 1996-2015, while no statistically significant change was observed in Common Pochard (41.8% and 39.5%, respectively). Both species showed a decline in breeding numbers over the same period. Severity of the preceding winter did not affect the proportion of females in the breeding area. Keywords Adult sex ratio • Aythya ferina • Aythya fuligula • Breeding population • Threatened species • Winter severity Zusammenfassung Geschlechterverhältnis zur Brutzeit bei zwei im Bestand abnehmenden Tauchentenarten: Variation zwischen den Jahren und Veränderungen über sechs Jahrzehnte Die Variation bezüglich des Geschlechterverhältnisses hat wichtige Konsequenzen für die Dynamik und Lebensfähigkeit von Populationen. Bei vielen Entenarten ist das Geschlechterverhältnis bei den Adulten zugunsten der Männchen verschoben, und Daten aus den Überwinterungsgebieten deuten darauf hin, dass diese "Männchenlastigkeit" bei manchen europäischen Entenarten zugenommen hat. Allerdings sind die den Änderungen im Geschlechterverhältnis zugrundeliegenden Ursachen bislang kaum erforscht und Informationen zur Geschlechterverhältnis-Variation bei Enten zur Brutzeit nur begrenzt verfügbar. Wir untersuchten langfristige Veränderungen des Geschlechterverhältnisses zur Brutzeit sowie der Brutvogelzahlen bei Tafelente Aythya ferina und Reiherente Aythya fuligula in Südfinnland; die erste Art wird in Finnland derzeit als "vom Aussterben bedroht", die letztere als "stark gefährdet" eingestuft. Zusätzlich überprüften wir die Hypothese, dass die jahresweise Variation des Geschlechterverhältnisses zur Brutzeit von der Härte der Wetterbedingungen in den Communicated by C. Barbraud.

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Section: Discussioncontrasting

confidence: 99%

Section: Discussionsupporting

confidence: 62%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Breeding sex ratios in two declining diving duck species: between-year variation and changes over six decades

Pöysä

Linkola²,

Paasivaara

2019

J Ornithol

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Long‐term trends and drought: Spatiotemporal variation in juvenile sex ratios of North American ducks

Ellis

Lohman

Sedinger

et al. 2022

Ecology and Evolution

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Sex ratios affect population dynamics and individual fitness, and changing sex ratios can be indicative of shifts in sex‐specific survival at different life stages. While climate and landscape changes alter sex ratios of wild bird populations, long‐term, landscape scale assessments of sex ratios are rare. Further, little work has been done to understand changes in sex ratios in avian communities. In this manuscript, we analyze long‐term (1961–2015) data on five species of ducks across five broad climatic regions of the United States to estimate the effects of drought and long‐term trends on the proportion of juvenile females captured at banding. As waterfowl have a 1:1 sex ratio at hatch, we interpret changes in sex ratios of captured juveniles as changes in sex‐specific survival rates during early life. Seven of 12 species‐region pairs exhibited evidence for long‐term trends in the proportion of juvenile females at banding. The proportion of juvenile females at banding increased for duck populations in the western United States and typically declined for duck populations in the eastern United States. We only observed evidence for an effect of drought in two of the 12 species‐region pairs, where the proportion of females declined during drought. As changes to North American landscapes and climate continue and intensify, we expect continued changes in sex‐specific juvenile survival rates. More broadly, we encourage further research examining the mechanisms underlying long‐term trends in juvenile sex ratios in avian communities.

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Associations between duck harvest, hunting wing ratios and measures of reproductive output in Northern Europe

et al. 2018

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Ducks are important game species, hunted in several countries throughout their annual cycle. We investigated whether the size of the annual duck harvest in Finland and Denmark reflected annual reproductive output in three common quarry duck species. Finland represents an important breeding area and Denmark important staging/wintering grounds for common teal (Anas crecca), Eurasian wigeon (Mareca penelope) and common goldeneye (Bucephala clangula). We assessed whether (i) annual duck harvest in these two countries correlated with variation in Finnish reproductive output or adult population size during 1990-2016 and (ii) variation in reproductive output of Finnish ducks was reflected in the juvenile ratios of birds harvested in Finland (2005-2007, 2014-2016) or Denmark (1990-2016). We hypothesised that variation in Finnish reproductive output would positively affect the size and juvenile ratio of the harvest, and that this effect would be stronger closer to the breeding grounds. Our data showed that the annual harvest of goldeneye in Finland was positively correlated with reproductive output, a desirable basis for applying sustainable management to this species. Teal and wigeon have much longer, more complex flyways, and their harvest did not mirror the annual production of young, although the wigeon harvest in Denmark increased with increasing juvenile ratio there. For these populations, we need to better define population units if we are to be able to assess harvest sustainability. We urgently need to monitor duck breeding success and harvest at larger spatial scales to support a comprehensive analysis of how well the harvest reflects reproductive output.

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Could falling female sex ratios among first‐winter northwest European duck populations contribute to skewed adult sex ratios and overall population declines?

Cited by 6 publications

References 37 publications

Breeding sex ratios in two declining diving duck species: between-year variation and changes over six decades

Breeding sex ratios in two declining diving duck species: between-year variation and changes over six decades

Long‐term trends and drought: Spatiotemporal variation in juvenile sex ratios of North American ducks

Associations between duck harvest, hunting wing ratios and measures of reproductive output in Northern Europe

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