Avian Ecology and Multi-Species Habitat Use in Pacific Coast Estuaries

Science Center Objects

Waterbirds such as shorebirds, waders, and ducks depend on healthy and productive estuaries to “fuel up” for long distance migrations along the Pacific Flyway.   Estuarine ecosystems include a mosaic of managed, natural, and restoring wetlands, and provide critical stop-over and wintering areas for federally protected migratory bird species. USGS WERC’s Dr. Susan De La Cruz works with federal, state, and local institutions to assess habitat use, foraging ecology, migratory connectivity and avian bioenergetics in California’s San Francisco Bay-Delta and across the Pacific Flyway. As part of the USGS mission to survey America’s natural resources, WERC scientists study avian health and their response to different environmental factors, be it invasive plants and predators, environmental pollutants, or human activity.

Hundreds of Pacific Flyway waterbird species rely on coastal estuaries during part or all of their annual cycle. However, these resource-rich areas are also under intense pressure from development and changing climate conditions.  USGS WERC researcher Dr. Susan De La Cruz links experimental field studies with statistical and geospatial modeling to evaluate threats and restoration benefits to migratory birds, their estuarine habitats, and their food resources.  Her collaborative work has the ultimate goal of identifying novel cross-seasonal approaches to further scientific understanding and inform the conservation of waterbirds throughout their ranges and across their annual cycles.  

WERC Greater Scaup in San Francisco Bay
Greater Scaup in San Francisco Bay. (Credit Susan De La Cruz/USGS. Public domain.)

Diving Duck Wintering Ecology

Surf scoter
Surf scoter (Melanitta perspicillata), a large sea duck that lives on the offshore waters of North America. (Credit USGS. Public domain.)

As the largest estuary on the Pacific Coast of North America, California’s San Francisco Bay-Delta is a critically important diving duck wintering area. Continentally, populations of bay and sea duck species such as lesser scaup and surf scoters have declined dramatically over the past three decades, while species such as canvasback have greatly fluctuated and redistributed in the Bay-Delta system.  Among several hypothesized reasons for these declines and redistributions are changes in habitat quality and quantity at wintering and spring stop-over sites. The Bay-Delta has lost more than 85% of its historical tidal marshes and has become a highly modified system with dramatically altered freshwater inflows.  Dr. De La Cruz and colleagues are currently conducting a multi-year, multi-species study to understand how seasonal habitat use and diet influences body condition, subsequent migration timing and reproductive potential of diving ducks in the Bay-Delta.   The results of this study will help to illuminate diving duck use of different food types and habitats in the Bay-Delta with the ultimate goal of identifying management and conservation strategies that may benefit these species.


Avian Health

USGS scientist holds tagged duckling
USGS scientist holds tagged duckling. (Credit David Nelson/USGS. Public domain.)

Avian influenza (AI) is regularly found in wild waterfowl and threatens both natural resources and human health. Although most AI strains are not deadly to poultry or humans, highly pathogenic (HPAI) strains of the virus have emerged in in the U.S. over the past few years. As part of a national prevention strategy, USGS WERC has worked as a domestic and international partner to target surveillance by sampling live-captured, apparently healthy wild birds to detect the presence of HPAI or antibodies to the virus. This effort targets bird species at the highest risk of exposure to HPAI. Over the past decade, USGS WERC, the USGS Alaska Science Center, USGS Patuxent Wildlife Research Center, and other partners have worked cooperatively on several AI projects on wild waterfowl in the U.S. and Asia to develop an eco-virological approach for studying this disease threat. Our current project objectives include determining the susceptibility of North American waterbird species to AI in the Central Valley and Bay-Delta of California and participating in efforts to understand the role of migratory birds in the spread of high and low pathogenic AI.

USGS scientist tagging duckling
USGS scientist tags a duckling for a waterfowl study. (Credit David Nelson/USGS. Public domain.)


Innovative Approaches:

Partnering with NASA to advance transmitter technology for wildlife tracking

The USGS SFBE is leading a collaborative effort among multiple USGS scientists and engineers at the NASA Ames Research Center to produce advanced GPS prototype tags. This unique partnership pairs USGS research and tagging expertise on diverse wildlife species with NASA’s cutting-edge engineering and nanotechnology expertise. Together, USGS and NASA hope to help researchers maximize the type and accuracy of data gained from the widest array of species and greatest number of individuals by reducing battery size, improving battery performance, integrating light-weight environmental sensors, and developing peer-to-peer network capability, which will enable two-way data exchange between tagged animals. USGS and NASA are taking an open‐hardware, open‐ software approach that aims to produce a low-cost design that can be adopted, modified, and improved by commercial providers, universities, and other government labs.

A miniaturized GPS tag developed in partnership with NASA
USGS and NASA collaborated to develop a prototype, miniaturized GPS tag to support wildlife biologists in their research. The new tag weighs about a third that of a house key. (Credit NASA. Public domain.)