For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment-visit https://www.usgs.gov or call 1-888-ASK-USGS (1-888-275-8747).For an overview of USGS information products, including maps, imagery, and publications, visit https://store.usgs.gov.The findings and conclusions in this article are those of the author(s) and do not necessarily represent the views of the U.S. Fish and Wildlife Service.Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Abstract Detecting populations of rare or cryptic species is essential for their conservation. For species like giant gartersnakes (Thamnophis gigas), conventional survey methods can be expensive and inefficient. These sampling difficulties might be overcome by modern techniques that detect deoxyribonucleic acid (DNA) shed by organisms into the environment (eDNA). We evaluated the efficacy of detecting giant gartersnake eDNA in water samples from the laboratory and at locations with known giant gartersnake populations in the Sacramento Valley of California, and failed to detect giant gartersnake DNA in most laboratory and all field samples. Aspects of giant gartersnake biology-such as highly keratinized skin and spending extensive time in the terrestrial environment, as well as hot, sunny, and turbid conditions in wetlands and canals of the Sacramento Valley-likely contributed to low detection probabilities. Although detection of eDNA shows promise under many conditions, further development is needed before sampling for eDNA is a viable option for detecting giant gartersnake populations.

ABSTRACT. Management actions to protect endangered species and conserve ecosystem function may not always be in precise alignment. Efforts to recover the California Ridgway's Rail (Rallus obsoletus obsoletus; hereafter, California rail), a federally and statelisted species, and restoration of tidal marsh ecosystems in the San Francisco Bay estuary provide a prime example of habitat restoration that has conflicted with species conservation. On the brink of extinction from habitat loss and degradation, and non-native predators in the 1990s, California rail populations responded positively to introduction of a non-native plant, Atlantic cordgrass (Spartina alterniflora). California rail populations were in substantial decline when the non-native Spartina was initially introduced as part of efforts to recover tidal marshes. Subsequent hybridization with the native Pacific cordgrass (Spartina foliosa) boosted California rail populations by providing greater cover and increased habitat area. The hybrid cordgrass (S. alterniflora × S. foliosa) readily invaded tidal mudflats and channels, and both crowded out native tidal marsh plants and increased sediment accretion in the marsh plain. This resulted in modification of tidal marsh geomorphology, hydrology, productivity, and species composition. Our results show that denser California rail populations occur in invasive Spartina than in native Spartina in San Francisco Bay. Herbicide treatment between 2005 and 2012 removed invasive Spartina from open intertidal mud and preserved foraging habitat for shorebirds. However, removal of invasive Spartina caused substantial decreases in California rail populations. Unknown facets of California rail ecology, undesirable interim stages of tidal marsh restoration, and competing management objectives among stakeholders resulted in management planning for endangered species or ecosystem restoration that favored one goal over the other. We have examined this perceived conflict and propose strategies for moderating harmful effects of restoration while meeting the needs of both endangered species and the imperiled native marsh ecosystem.

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Studying migration is critically important for understanding the full-annual cycle of migrating birds and aids in management and conservation. In recent years, global positioning system (GPS) and platform transmitting terminal (PTT) tags have become miniaturized, revolutionizing migration research by allowing for higher location accuracy and global coverage for smaller species. We reviewed 116 primary research papers from 2006 to 2021 that reported on GPS- or PTT-tagged small birds (<500 g) during migration and assessed research aims, tag efficacy, ecological findings, and future opportunities. Reviewed papers covered 58 unique species (nearly half of which were shorebirds) and 65% of studies tagged birds at breeding grounds. Tags that did not require retrieval had higher success obtaining data, with PTT tags having the greatest success (85% of deployed tags had data). Of studies that reported tag load information, most (70%) reported tag loads ≥3% body mass, which is a potential concern given that 3% is considered the preferable upper limit. Most papers (69%) focused on presenting spatial information such as migratory routes, stopover sites, and habitat use, and only 33% of papers tested explicit hypotheses, demonstrating that we are in the early stages of understanding small bird migration at fine scales. Almost all tag deployments (93%) occurred in the northern hemisphere, most often in the United States (24%), indicating a deficiency in GPS and PTT research on small bird migration from the southern hemisphere. GPS and PTT tags have revealed new biological insights not possible with other technologies by providing fine-scale movement data and global coverage. There are exciting opportunities for researchers to move beyond descriptive spatial studies and explore hypothesis-driven migratory research, into topics such as intraspecific variation, carry-over effects, and climate-driven movements for irruptive species.

By the mid-20th Century, giant gartersnakes (Thamnophis gigas) had lost more than 90% of their Central Valley marsh habitat and were extirpated from more than two-thirds of their range. This massive habitat loss led to their inclusion in the inaugural list of rare species under the California Endangered Species Act (CESA). Listing under the CESA provided giant gartersnakes legal protection and mechanisms for recovery, and subsequent listing under the U.S. Endangered Species Act (federal ESA) further fortified these protections. But how effective has listing under these endangered species acts (ESAs) been at achieving their goal of giant gartersnake recovery? Herein, we review relevant aspects of giant gartersnake ecology, illustrate how listing has benefited giant gartersnakes and what challenges have been faced in slowing declines and recovering populations, and chart a course toward improved conservation, management, and recovery of giant gartersnakes. Although listing as threatened under both state and federal ESAs has not yet achieved recovery of giant gartersnakes, the increased knowledge gained and mechanisms for protecting giant gartersnake habitat on private and public lands developed over the past 50 years has improved conservation of this endemic California snake.