Ethan J. Royal | Geology Reports

USGS2025

Apparent annual survival of adult Golden-winged Warblers (Vermivora chrysoptera) may not differ by sex or region

Understanding range-wide demographic, spatial, and temporal variation in annual survival is essential for managing species of conservation concern. Multi-population models are useful tools for integrating diverse datasets, reducing biases, and deriving survival estimates across differing spatial scales. We conducted a range-wide, multi-population apparent annual survival analysis for a declining songbird, Vermivora chrysoptera (Golden-winged Warbler), using data from 18 sites across its breeding and nonbreeding grounds. This Nearctic-Neotropical migrant breeds in 2 disjunct regional populations, the Great Lakes and Appalachian Mountains, which are experiencing different rates of decline. We aimed to quantify regional-, site-, and sex-specific apparent annual survival estimates to identify geographic patterns or demographic factors influencing population declines. We used simulations to assess the precision of our estimates. Our models did not reveal a substantial difference in apparent annual survival between the Great Lakes (0.41, 95% credible interval (CrI):0.31–0.50) and the Appalachian regions (0.49, 95% CrI: 0.36–0.60), as CrIs overlapped. Site-specific estimates also showed no clear differences in apparent annual survival among sites representing both regional populations. Male apparent annual survival tended to be greater than female apparent annual survival in both regions, though CrI’s overlapped. Our study suggests demographic factors other than adult annual survival likely play a larger role in recent regional and range-wide population declines, such as productivity, juvenile/immature survival, or recruitment. Simulations indicate that improving recapture probability and study duration of datasets could lead to more precise apparent annual survival estimates. However, our model produced CrI ranges comparable to the most ideal data collection scenario, suggesting the lack of trends we found was not due to variability in our estimates. We stress the importance of addressing inherent biases in survival datasets and the need for standardized collaborative efforts to inform species conservation on a range-wide scale.

Ornithology↗

USGS2024

Ecology of an insular snake assemblage in coastal Maine

Wildlife populations at the peripheries of their distributions or on isolated islands often display divergent and poorly understood morphological or life-history characteristics compared to core populations. We used a capture–mark–recapture dataset collected over a 19-year period to characterize a northern, insular snake assemblage in coastal Maine. We captured 611 individual snakes of 4 species ( Thamnophis sirtalis [Common Gartersnake; n = 221 individuals], Diadophis punctatus [Ring-necked Snake; n = 258 individuals], Storeria occipitomaculata [Red-bellied Snake; n = 81 individuals], and Opheodrys vernalis [Smooth Greensnake; n = 51 individuals]) and recorded 104 recaptures. We provide some of the first data on growth, reproduction, and movement for these species in northern New England, expanding our understanding of insular and northern snake populations. Specifically, we found that Common Gartersnakes fed primarily on earthworms and amphibians and grew rapidly, in accordance with mainland populations, but exhibited smaller size at maturity and average litter sizes. We captured an unusually large number of Ring-necked Snakes, which are uncommon elsewhere in Maine, and recorded an apparently localized nesting area for this species, as well as relatively long-distance (230–300 m) dispersal away from that location. In our population, female Ring-necked Snakes mature in their third year, and this species exhibits weak sexual size dimorphism (SSD). We found the ecology of Red-bellied Snakes at our study site to be similar to other populations, with individuals feeding on slugs, and females maturing in their second year; however, our population exhibited the strongest pattern of (female-biased) SSD. Smooth Greensnakes were restricted to the most extensive old-field habitat within our study site and fed on a variety of arthropods. We confirmed communal nesting and short incubation period for this species and provide among the first data on growth and longevity (at least 7 years) of this relatively understudied species.

Maine↗