Cory Overton
Science and Products
Goose Population Dynamics in the California Central Valley and Pacific Flyway
USGS scientists and partners are studying how growing goose populations in the California Central Valley wintering areas are affecting ducks and other waterfowl.
The Impact of Drought on Waterbirds and Their Wetland Habitats in California’s Central Valley
California’s Central Valley is a nexus for water resources in the state, draining the Sacramento and San Joaquin River watersheds. Urban centers, agricultural operations, and the environment all compete for limited water, and demand is expected to only increase as the population grows and agriculture intensifies. At the same time, the water supply is projected to decrease as temperatures rise...
Effects of Sea-Level Rise and Extreme Storms on California Coastal Habitats: Part 1
In California, the near-shore area where the ocean meets the land is a highly productive yet sensitive region that supports a wealth of wildlife, including several native bird species. These saltmarshes, mudflats, and shallow bays are not only critical for wildlife, but they also provide economic and recreational benefits to local communities. Today, sea-level rise, more frequent and stronger...
Fate of Endangered Species in San Francisco Bay Tidal Marshes with Sea-Level Rise
The San Francisco Bay estuary contains the largest remaining expanse of tidal salt marshes in the western U.S. These marshes are home to a variety of federal and state protected species, such as the California clapper rail, California black rail, and the salt marsh harvest mouse. The estuary is also located on the Pacific Flyway, and is an important site for migrating and wintering birds. As...
Good prospects: High-resolution telemetry data suggests novel brood-site selection behavior in waterfowl
Breeding success should increase with prior knowledge of the surrounding environment, which is dependent upon an animal’s ability to evaluate habitat. Prospecting for nesting locations and migratory stop-over sites are well-established behaviors among bird species. We assessed whether ducks in Suisun Marsh, California, USA, a brackish marsh,...
Casazza, Michael L.; McDuie, Fiona; Lorenz, Austen; Keiter, David A.; Yee, Julie L.; Overton, Cory T.; Peterson, Sarah H.; Feldheim, Cliff L.; Ackerman, Joshua T. Moving at the speed of flight: Dabbling duck-movement rates and the relationship with electronic tracking interval
Context. Effective wildlife management requires information on habitat and resource needs, which can be estimated with movement information and modelling energetics. One necessary component of avian models is flight speeds at multiple temporal scales. Technology has limited the ability to accurately assess flight speeds, leading to estimates of...
McDuie, Fiona; Casazza, Michael L.; Keiter, David A.; Overton, Cory T.; Herzog, Mark P.; Feldheim, Cliff L.; Ackerman, Joshua T. GPS tracking data reveals daily spatio-temporal movement patterns of waterfowl
BackgroundSpatio-temporal patterns of movement can characterize relationships between organisms and their surroundings, and address gaps in our understanding of species ecology, activity budgets, bioenergetics, and habitat resource management. Highly mobile waterfowl, which can exploit resources over large spatial extents, are excellent models to...
McDuie, Fiona; Casazza, Michael L.; Overton, Cory T.; Herzog, Mark P.; Hartman, C. Alex; Peterson, Sarah H.; Feldheim, Cliff L.; Ackerman, Joshua T. Rising tides: Assessing habitat vulnerability for an endangered salt marsh-dependent species with sea-level rise
Salt marsh-dependent species are vulnerable to impacts of sea-level rise (SLR). Site-specific differences in ecogeomorphic processes result in different SLR vulnerabilities. SLR impacts to Ridgway’s rail (Rallus obsoletus) of Southern California (SC) and San Francisco Bay (SF), U.S.A. could foreshadow SLR effects on other coastal endemic species....
Rosencranz, Jordan A.; Thorne, Karen M.; Buffington, Kevin J.; Overton, Cory T.; Takekawa, John; Casazza, Michael L.; McBroom, Jennifer; Wood, Julian K.; Nur, Nadav; Zembal, Richard L.; MacDonald, Glen M.; Ambrose, Richard F. Duck nest depredation, predator behavior, and female response using video
Depredation plays an important role in determining duck nest success and predator and female duck behavior during nest depredation can influence nest fate. We examined depredation of mallard (Anas platyrhynchos) and gadwall (A. strepera) nests in Suisun Marsh, California, USA, in 2015–2016 with continuous infrared video monitoring to identify nest...
Croston, Rebecca; Ackerman, Joshua T.; Herzog, Mark P.; Kohl, Jeffrey D.; Hartman, C. Alex; Peterson, Sarah H.; Overton, Cory T.; Feldheim, Cliff L.; Casazza, Michael L. Lessons from the past: isotopes of an endangered rail as indicators of underlying change to tidal marsh habitats
Introduction: Tidal marsh systems along the Pacific coast of the United States have experienced substantial stress and loss of area and ecosystem function, which we examined by using the endangered California Ridgway’s Rail, Rallus obsoletus obsoletus (‘rail’) as an indicator of its tidal marsh habitat in the San Francisco Estuary....
Merritt, Angela M.; Casazza, Michael L.; Overton, Cory T.; Takekawa, John Y.; Hahn, Thomas P.; Hull, Joshua M. Environmental extremes and biotic interactions facilitate depredation of endangered California Ridgway’s rail in a San Francisco Bay tidal marsh
On 23 December 2015 while performing a high tide population survey for endangered Ridgway’s rails (Rallus obsoletus obsoletus; formerly known as the California clapper rail) and other rail species at Arrowhead Marsh, Martin Luther King Jr. Regional Shoreline, Oakland, California, the authors observed a series of species interactions resulting in...
Overton, Cory T.; Bobzien, Steven; Grefsrud, Marcia A century of landscape disturbance and urbanization of the San Francisco Bay region affects the present-day genetic diversity of the California Ridgway’s rail (Rallus obsoletus obsoletus)
Fragmentation and loss of natural habitat have important consequences for wild populations and can negatively affect long-term viability and resilience to environmental change. Salt marsh obligate species, such as those that occupy the San Francisco Bay Estuary in western North America, occupy already impaired habitats as result of human...
Wood, Dustin A.; Bui, Thuy-Vy D.; Overton, Cory T.; Vandergast, Amy G.; Casazza, Michael L.; Hull, Joshua M.; Takekawa, John Y. Depredation of the California Ridgway’s rail: Causes and distribution
We studied the causes of mortality for the California Ridgway’s rail at multiple tidal marshes in the San Francisco Bay Estuary, California. We radio-marked 196 individual rails and examined the evidence from 152 recovered California Ridgway’s rail mortalities from our radio-marked sample and determined plausible cause of death from a wide array...
Casazza, Michael L.; Overton, Cory T.; Bui, Thuy-Vy D.; Takekawa, John Y.; Merritt, Angela M.; Hull, J.M. Endangered species management and ecosystem restoration: Finding the common ground
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 state-listed species, and restoration of tidal marsh ecosystems in the San Francisco Bay estuary...
Casazza, Michael L.; Overton, Cory T.; Bui, Thuy-Vy D.; Hull, Joshua M.; Albertson, Joy D.; Bloom, Valary K.; Bobzien, Steven; McBroom, Jennifer; Latta, Marilyn; Olofson, Peggy; Rohmer, Tobias M.; Schwarzbach, Steven E.; Strong, Donald R.; Grijalva, Erik; Wood, Julian K.; Skalos, Shannon; Takekawa, John Y. Integrating spatially explicit indices of abundance and habitat quality: an applied example for greater sage-grouse management
Predictive species distributional models are a cornerstone of wildlife conservation planning. Constructing such models requires robust underpinning science that integrates formerly disparate data types to achieve effective species management. Greater sage-grouse Centrocercus urophasianus, hereafter “sage-grouse” populations are...
Coates, Peter S.; Casazza, Michael L.; Ricca, Mark A.; Brussee, Brianne E.; Blomberg, Erik J.; Gustafson, K. Benjamin; Overton, Cory T.; Davis, Dawn M.; Niell, Lara E.; Espinosa, Shawn P.; Gardner, Scott C.; Delehanty, David J. Science foundation Chapter 5 Appendix 5.1: Case study california ridgway's rail (Rallus obseoletus obsoletus)
The clapper rail (Rallus longirostris) recently was split into two sister groups (Chesser et al. 2014) on the basis of phylogenetic analyses (Maley and Brumfield 2013). The original grouping is now represented on the East Coast of North America by the Clapper rail (Rallus crepitans) and on the West Coast by the Ridgway’s rail (Rallus obsoletus)....
Overton, Cory T.; Wood, Julian