Long-term trends and drought: spatiotemporal variation in juvenile sex ratios of North American ducks

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.

Systematic Review of Bird Response to Privately-Owned, Managed Pine Stands in the Southeastern U.S.

The southeastern U.S. is widely known as a bastion of privately-owned, managed pine (Pinus spp.) forests, comprised primarily of native pine species. The region supports high levels of biodiversity, but also a multi-billion-dollar forest products economy critical to socioeconomic stability of rural areas. We conducted a systematic review of studies focused exclusively on avifaunal associations within privately-owned, managed pine landscapes in the southeastern U.S. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analysis framework to examine all available studies that evaluated aspects of avian diversity, abundance, and community composition across a suite of forest types, stand ages, and forest management practices within southeastern managed pine systems in the last 70 years. We screened 160 records through primary database searches, and 1696 secondary records from supplemental searches and other sources, and identified 103 relevant articles for inclusion. As expected, although there is no single forest management practice that best provides for avian communities, we found practices that: (1) involve prudent site preparation; (2) promote forest thinning and intermediate management practices; (3) provide non-pine vegetative cover; (4) supply fine- and meso-filter resources such as retained snags and coarse woody debris; and (5) promote heterogeneity in cover types, largely enhanced value of southeastern managed pine systems to avian communities. Overall, it appears that avian communities can be best maintained by providing a diverse mosaic of forest conditions in managed pine landscapes. Key research gaps include improving understanding avian population demographics, such as survival, reproduction, and dispersal.