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-change 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
analyse 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 twelve
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
twelve 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.
Warning on nine Pollutants and their effects on avian communities
