Indicator
Waterfowl Population Sites
2023 Evaluation
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This indicator measures the protection of waterfowl population sites such as marshes in the Tahoe Region. These sites support waterfowl species such as those in the Anatidae (i.e., ducks and geese), Ardeidae (e.g., herons), and Sternidae (i.e., terns) families, as well as water birds such as the eared grebe, marsh wren, and Virginia rail. The Tahoe Region supports breeding waterfowl, serves as a stopover for waterfowl migrating along the Pacific Flyway, and is an important component of functioning wetland ecosystems. Waterfowl sites in the Tahoe Region are mostly impacted by recreation. Regional programs that protect marshes and wetlands from being developed and reduce recreation impacts aim to protect waterfowl population sites. TRPA monitors waterfowl population sites by analyzing the development and human activity impacts. 

Waterfowl Population Sites.jpg
Status

Average "Human Disturbance Ratings" of 18 mapped waterfowl population sites. Sites are ranked from one to four, with one being the least disturbed and four being the most disturbed. A higher score represents higher human activity levels.

Data provided by TRPA. Access detailed datasets on Tahoe Open Data, including: Waterfowl Habitat and Annual Data.

2023 Evaluation
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Status
At or Somewhat Better Than Target
Trend
Little or No Change
Confidence
Low
Applicable Standard
W7: Provide a minimum of 18 Waterfowl population sites. W14: Provide disturbance zones and influence zones areas for Waterfowl.
Key Points
  • Eighteen designated waterfowl sites are mapped and none have been altered by development.
  • Increases in recreation impacts are leading to greater disturbances at waterfowl sites. Several agencies have completed projects to reduce impacts from recreation through fencing and seasonal closures.
  • The disturbance zone standard for waterfowl sites has been implemented by TRPA and other partner agencies.
Evaluation Map
Description

A map showing the the locations of TRPA-designated waterfowl population sites around the Tahoe Basin.

About the Threshold
The TRPA definition of special interest waterfowl includes species in the Anatidae (i.e., ducks and geese), Ardeidae (e.g., herons), and Sternidae (i.e., terns) families (TRPA 1982b). Protecting habitat for waterfowl also protects habitat for other water birds such as the eared grebe, marsh wren, and Virginia rail (TRPA 2007). The Tahoe Basin supports breeding waterfowl and serves as a stopover for waterfowl migrating along the Pacific Flyway. Many waterfowl species are valued for wildlife viewing and hunting, and collectively they are an important component of functioning wetland ecosystems. Waterfowl are dependent on various biological, chemical, and physical aspects of wetlands for their survival, so their use of a site can serve as an indicator of the biological integrity or relative value of a site for providing a functioning wetland ecosystem.
Many of the mapped waterfowl population sites coincide with recreation destinations (e.g., beaches, golf courses, community parks, and off-highway vehicle and hiking trails). Recreational uses have been demonstrated to reduce reproductive success by causing nest abandonment, decreased hatching success, and reduced survivorship of hatchlings; and can cause mortality by increasing energy expenditures and reducing foraging success (Korschgen and Dahlgren 1992; Knight and Gutzwiller 1995). Physical habitat conditions, such as the type and configuration of vegetation communities and area of open water are good predictors of bird species richness within the basin (Schlesinger and Romsos 2000), so alterations to these physical characteristics could affect waterfowl use of a site. Habitat requirements vary by waterfowl species, but the amount, diversity, and level of alterations to wetlands may be a driver of waterfowl populations (Batt et al. 1992). Historic land uses, such as the filling of large portions of the Upper Truckee Marsh for construction of the Tahoe Keys in the 1960s, has also greatly reduced the amount of waterfowl habitat within the Tahoe Basin. Waterfowl populations in the basin may also be affected by annual and seasonal changes in the availability of food at local, regional and national scales, which can be influenced by weather (e.g., drought). Temporary food scarcity can reduce reproductive success or cause waterfowl to use other areas with more available food resources (Batt et al. 1992).
Delivering and Measuring Success

EIP Action Priorities

EIP Indicators

Example EIP Projects

  • Upper Truckee River and Marsh Restoration

    This project restores and enhances over 250 acres of floodplain by returning river flows to the center of the marsh. Returning river flows to the marsh will enrich native fish and bird habitat.

Monitoring Programs

Rationale Details
At or Somewhat Better Than Target. The current status of waterfowl population sites was determined by analyzing whether the site has been developed and the current human activity impacts. No waterfowl population sites have been lost. Therefore, the current status is at or somewhat better than target.
Little or No Change. Trend is determined by comparing the number of existing sites through the years and comparing human activity rating scores. Little or no change has been observed.
Confidence Details
Moderate. Standardized protocols were used and it is clear that no waterfowl population sites have been lost to development, but the monitoring protocol focuses on levels of human disturbance, rather than on waterfowl populations.
Low. Confidence that there have been no changes in the number of waterfowl population sites, the overall trend in condition at these sites is mostly unknown to due to limited data.
Low. If one confidence rating is moderate and the other is low, the overall confidence rating is the lower confidence rating.
Additional Figures and Resources

No photos available.

No documents available.