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Home Water Aquatic Species and Communities

Waterfowl

Status and Trend

Interpretation and Commentary

Status: Somewhat Worse Than Target
Trend: Moderate Improvement
Confidence: Low

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Status
Site Name Score
Grass Lake 1
Lily Lake 1
McKinney Lake 1
Osgood Swamp 1
Lake Christopher 2
Lower Echo Lake 2
Pope Marsh 2
Spooner Lake 2
Truckee Marsh 2
Upper Echo Lake 2
Baldwin Marsh 2
Blackwood Canyon 2
Bliss Pond 2
North Fallen Leaf Lake 3
Taylor Creek Marsh 3
Edgewood Golf Course 4
Fannette Island 4
Lake Baron 4

Recreational impact and habitat intactness score for the 18 waterfowl threshold sites. Sites are ranked 1 to 4 with 1 being the most intact and 4 being the most disturbed.

  • Relevance - Waterfowl consist of numerous species in the family Anatidae (i.e., ducks and geese). Protecting habitat for waterfowl also protects habitat for other water birds such as the American Bittern, Eared Grebe, Marsh Wren, and Virginia Rail (TRPA 2007c). 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 aspects of wetlands for their survival, so they serve as one indicator of the biological integrity of wetland ecosystems.
  • Adopted Standards - Protect a minimum of 18 waterfowl population sites.
  • Indicator - The status and trend determination is based on a qualitative assessment of habitat condition and recreation impacts, and a review of management actions that could affect waterfowl at the 18 mapped waterfowl sites. Some previous evaluations have also used a comparison of the species richness of waterfowl, water bird, and detrimental or non-native species (e.g. Brown-headed Cowbird, European Starling) (TRPA 2001; TRPA 2007c).
  • Status – The status and trend determination is based on a qualitative assessment of habitat condition and recreation impacts, and a review of management actions that could affect waterfowl at the 18 mapped waterfowl sites. Some previous evaluations have also used a comparison of the species richness of waterfowl, water bird, and detrimental or non-native species (e.g. Brown-headed Cowbird, European Starling) (TRPA 2001; TRPA 2007c).
     

  • Trend The habitat assessment showed an improved score for the Blackwood Canyon site when compared to the previous assessment that was conducted in 2001. This improvement is the result of the U.S. Forest Service completing a large-scale restoration project, and blocking motorized access into the meadow. No other scores changed since the 2001 habitat assessment, but several management actions have occurred that should lead to improved habitat conditions. At the Truckee Marsh site, the CTC recently instituted a seasonal dog closure during the peak breeding season, which is expected to improve habitat use and reproductive success by waterfowl. At the Osgood Swamp site, the U.S. Forest Service decommissioned a trail accessing the wetland, reducing human incursions into the site. During the habitat assessment, no indications of substantial increased levels of disturbance were noted at any of the waterfowl sites. Therefore, there is an improving trend in the habitat condition of waterfowl sites.
     

  • Confidence – The confidence in the status and trend is low. No comprehensive waterfowl surveys have been conducted since the last Threshold Evaluation in 2006, so status and trend determinations are based solely on habitat evaluations and recent management actions. The habitat evaluations and review of management actions provide information on the physical condition of waterfowl habitat and the level of human disturbance, but they provide less information than direct measures of waterfowl use at the sites. Other factors that are not measured by the habitat evaluations could be affecting waterfowl populations.
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  • Human and Environmental Drivers - Many areas of waterfowl habitat in Tahoe experience significant recreational use. This use can reduce reproductive success by leading to nest abandonment, decreased hatching success, and reduced survivorship of hatchlings; and can cause mortality in non-breeding waterfowl by increasing energy expenditures and reducing foraging success (Korschgen and 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 waterfowl species richness in Tahoe (Schlesinger and Romsos 2000), so alterations to these physical characteristics would likely affect waterfowl. Specific habitat requirements vary for different waterfowl species, but the amount, diversity, and level of alterations to wetlands may be a driver of waterfowl populations (Batt et al.1992).Waterfowl populations in Tahoe may also be affected by annual and seasonal changes in the availability of food, which can be influenced by weather. This temporary food scarcity can reduce reproductive success or cause waterfowl to relocate to areas with more available food sources (Batt et al.1992).
  • Monitoring Approach – For the qualitative habitat assessment, biologists rank each waterfowl site on a scale of 1 to 4 based on observations of recreational impacts and intactness of habitat. For the waterfowl surveys, which were not completed during this evaluation period, biologists conduct breeding bird observations for three to four one-hour periods at each mapped waterfowl habitat site. All breeding bird species are recorded and the species richness of waterfowl, water birds, songbirds, and species that are indicative of disturbance or detrimental to waterfowl are compared.

  • Monitoring Partners – US Forest Service, TRPA

Links

 
  • Monitoring Plan
  • Conceptual Model

Map


 

Map of the Tahoe Basin showing the location and name of the 18 waterfowl designated by TRPA as population sites.

Additional Info

References

Additional Information

Last Updated on Wednesday, 03 October 2012 10:07