Adults have more male-biased sex ratios than first-winter juveniles in wintering duck populations

Background:The long-term monitoring of demographic changes in waterbird populations remains limited,but such information can be valuable for conservationists and waterbird managers.Biased sex ratios can indicate differences in survival rates between sexes.In particular,differences in the sex ratios of fledged juveniles and adults can provide insight into the development of male bias among populations.Methods:In this study,we used data from individual birds captured over a 57-year period to assess the extent,and temporal variability in male bias in nine populations of ducks wintering in the United Kingdom:Gadwall(Mareca strepera),Northern Mallard(Anas platyrhynchos),Northern Pintail(Anas acuta),Common Pochard(Aythya ferina),Common Shelduck(Tadorna tadorna),Northern Shoveler(Spatula clypeata),Eurasian Teal(Anas crecca),Tufted Duck(Aythya fuligula),and Eurasian Wigeon(Mareca penelope).Results:Overall,eight of these populations were significantly male-biased and adults were more male-biased than first-winter juveniles for all nine populations.The increased male bias among adults is consistent with the hypothesis that factors such as higher mortality of reproductive-age females during the breeding season is a major cause of male bias in duck populations.However,such predation cannot explain the male bias detected in first-winter juveniles in four of the populations.The temporal trends in male bias differed between adults and first-winter juveniles in Northern Mallard,Northern Pintail,Common Pochard,Common Shelduck,Eurasian Teal,Tufted Duck,and Eurasian Wigeon.Over the study period we found increased male bias among adult Northern Mallard,Northern Pintail,Common Pochard,Common Shelduck,and Tufted Duck as well as both adult and first-winter juvenile Northern Shoveler.Conclusions:We provide evidence that among wintering duck populations,sex ratios are typically male-biased,with adults exhibiting stronger male-biased sex ratios than first-winter juveniles.Improved monitoring of sex ratios of wintering waterbirds would help to increase our understanding of changes in waterbird demography,population structure,and observed population trends;our study shows that birds caught during ringing projects can be a valuable source of such data.

Epidemic of wild-origin H1NX avian influenza viruses in Anhui,China

Background:As the natural hosts of avian influenza viruses(AIVs),aquatic and migratory birds provide a gene pool for genetic transfer among species and across species,forming transient“genome constellations.”This work describes the phylogenetic dynamics of H1NX based on the complete molecular characterization of eight genes of viruses that were collected from 2014 to 2015 in Anhui Province,China.Methods:Hemagglutination and hemagglutination inhibition tests were used to determine the hemagglutination(HA)activity of the HA subtypes.The entire genomes of the viruses were sequenced on an ABI PRISM 3500xl DNA Analyzer.The sequences were genetically analysed to study their genetic evolution using DNASTAR and MEGA 6.The pathogenic effects of the viruses were evaluated using mouse infection models.Results:Seven strains of the H1 subtype avian influenza virus were isolated.Phylogenetic analysis indicated natural recombination of the H1 influenza viruses between the Eurasian lineage and the North American lineage.Some genes had high sequence identity with A/bean goose/Korea/220/2011(H9N2),which is a typical case involving viral reassortment between the Eurasian lineage and the North American lineage.The results of infection experiments in mice showed that the viruses could acquire the ability to multiply in mouse respiratory organs without adaptation.Conclusions:These findings suggest that continued surveillance of wild birds,particularly migratory birds,is important to provide early warning of possible H1 influenza epidemics and to understand the ecology of the virus.