Search USGS⌕ Search
Home/Archive/USGS

USGS · 70035348

Population variation in isotopic composition of shorebird feathers: Implications for determining molting grounds

J. Torres-Dowdall·A.H. Farmer·E.H. Bucher·R. O. Rye·G. Landis
View original source ↗Export metadata ↓

Abstract

Stable isotope analyses have revolutionized the study of migratory connectivity. However, as with all tools, their limitations must be understood in order to derive the maximum benefit of a particular application. The goal of this study was to evaluate the efficacy of stable isotopes of C, N, H, O and S for assigning known-origin feathers to the molting sites of migrant shorebird species wintering and breeding in Argentina. Specific objectives were to: 1) compare the efficacy of the technique for studying shorebird species with different migration patterns, life histories and habitat-use patterns; 2) evaluate the grouping of species with similar migration and habitat use patterns in a single analysis to potentially improve prediction accuracy; and 3) evaluate the potential gains in prediction accuracy that might be achieved from using multiple stable isotopes. The efficacy of stable isotope ratios to determine origin was found to vary with species. While one species (White-rumped Sandpiper, Calidris fuscicollis) had high levels of accuracy assigning samples to known origin (91% of samples correctly assigned), another (Collared Plover, Charadrius collaris) showed low levels of accuracy (52% of samples correctly assigned). Intra-individual variability may account for this difference in efficacy. The prediction model for three species with similar migration and habitat-use patterns performed poorly compared with the model for just one of the species (71% versus 91% of samples correctly assigned). Thus, combining multiple sympatric species may not improve model prediction accuracy. Increasing the number of stable isotopes in the analyses increased the accuracy of assigning shorebirds to their molting origin, but the best combination - involving a subset of all the isotopes analyzed - varied among species.

Explore related subjects

WaterbirdsArticle

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

J. Torres-Dowdall, A.H. Farmer, E.H. Bucher, R. O. Rye, G. Landis. 2009. Population variation in isotopic composition of shorebird feathers: Implications for determining molting grounds. https://doi.org/10.1675/063.032.0210

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2025

Effects of nest exclosure on nest and adult survival of piping plover (Charadrius melodus) in the lower Platte River System, Nebraska

Conservation of imperiled species often includes management strategies intended to improve specific vital rates. However, some management practices can have unforeseen consequences that negate the intended benefit. For example, nest exclosures are often used for ground-nesting avian species to reduce nest predation but may increase depredation of adults. Tradeoffs between nest survival and adult mortality of nest exclosures likely depend on local predator community dynamics. Therefore, investigations are most informative when assessed in specific settings. Piping Plovers ( Charadrius melodus , hereafter plovers) in the lower Platte River system, Nebraska, nest at off-river sandpit sites, which provide an additional study system and habitat to assess the context-dependent effects of nest exclosures. The Tern and Plover Conservation Partnership monitors plovers at off-river sites by monitoring nests, installing nest exclosures, and banding and resighting. Effects of nest exclosures were tested on both nest survival, from 340 plover nests from 2008–2024, and weekly within-season apparent survival, from 71 breeding adults from 2011–2024. There was weak evidence that nest exclosures marginally improved nest survival but no evidence of an effect for within-season survival of breeding adults. Daily nest survival was slightly higher for exclosed nests (0.99, [85% CI = 0.98–0.99]) than unexclosed nests (0.98, [0.98–0.99]). Within-season apparent weekly survival for breeding plovers was 0.90 (95% CI = 0.83–0.93); cumulative survival over the breeding period was 0.51 (0.33–0.69). Nest exclosures may be used to increase nest survival at off-river sites with minimal threat to adult survival unless considerable concerns arise.

Nebraska↗
USGS2025

Variation in detection distance of Eastern Black Rail (Laterallus jamaicensis jamaicensis) vocalizations by autonomous recording units

Autonomous recording units (ARUs) are an emerging technology that allows for passive monitoring of soniferous animals and soundscapes. Over the past decade, ARUs have become a popular tool for monitoring birds for their potential to reduce the labor and costs of traditional in-person sampling procedures. However, uncertainty surrounding factors affecting detection of avian taxa using ARUs can inhibit their monitoring efficacy. Eastern Black Rails ( Laterallus jamaicensis jamaicensis ) are a secretive marsh bird listed as a federally threatened species in the U.S.A. Eastern Black Rail vocalizations are difficult to detect by field personnel, and numerous in-person surveys can be required to confirm their presence at a site. While ARUs are an alternative for detecting Eastern Black Rails, it is unknown at what maximum distance an ARU can detect their vocalizations. We evaluated factors affecting the detection distance of simulated vocalizations for ARUs in four marsh vegetation types under a range of environmental conditions. Detection distances varied across models, vocalization and vegetation types, and call volume. Kickeedo vocalizations were detected at greater distances, and detection distances increased for all vocalization types in open vegetation. High relative humidity increased detection distances, while louder background noise decreased detection distances. High wind speeds in cordgrass ( Spartina spp .) decreased detection probability disproportionately relative to other vegetation types. Based on these results, considerations of survey area, vegetation type, and site condition can allow land managers and researchers to optimize Eastern Black Rail monitoring using ARUs. Given the substantial staff time needed to monitor this species, ARUs may increase the likelihood of detection and provide an efficient alternative to in-person monitoring.

Waterbirds↗
USGS2023

eDNA Metabarcoding Analyses of Diet in Yellow-Billed Loons of Northern Alaska

Environmental DNA is a burgeoning tool used to address wide-ranging scientific questions, including determining diets of difficult-to-sample predators. Loons are large piscivorous diving birds that capture and consume prey underwater, making it nearly impossible to visually determine their diet via observation alone. Identifying species' diets is important for understanding basic life history traits, and revealing key prey species can clarify species' roles in complex trophic webs, aid in understanding population and community dynamics, and help identify critical habitat for protection. Current information about loon diet is largely anecdotal, and traditional non-observational methods for quantifying loon diet have limitations. Analysis of eDNA from loon feces may provide biologists with a non-invasive technique for determining diet without negative sampling effects, and with increased resolution as compared to other techniques. We surveyed lakes in two areas of northern Alaska for Yellow-billed Loons ( Gavia adamsii ). Loon fecal samples were collected opportunistically from latrine sites without disturbing any animals and analyzed using novel marker sets to determine loon species and diet. Fish species were detected in all fecal samples, the most common being Alaska blackfish ( Dallia pectoralis ), and ninespine stickleback ( Pungitius pungitius ). This research demonstrates that eDNA metabarcoding analyses of loon fecal samples can determine the specific loon species that deposited the feces and characterize the piscine portion of their diet with limited disturbance to the animals.

Alaska↗