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This indicator measures the number of active osprey nests in the Tahoe Region. The osprey (Pandion haliaetus) is a conspicuous large raptor that is valued for wildlife viewing. Human disturbance near nesting and foraging areas can impact osprey breeding success. Regional programs that limit forest fire fuel reduction activities around known nests and preserve large snags aim to protect the osprey population. TRPA actively monitors osprey populations across the Tahoe Region with various partners.
- Status
- Considerably Better Than Target
- Trend
- Rapid Improvement
- Confidence
- High
- The osprey population has increased substantially since the early 1980's when only a few nests were active in the Tahoe Basin.
- In the last five years, the number of active nests has varied but remains stable.
- The shoreline from Emerald Bay to DL Bliss State Park and the undeveloped portions of the East Shore are the main reproductive areas for osprey.
- The disturbance zone standard for osprey has been implemented by TRPA and other partner agencies.
- Potential disturbances such as new trails and forest fuels reduction projects are adjusted to protect nesting osprey.
Appoximate locations of all recorded osprey nests in the Tahoe Basin (2015 through 2019).
- The osprey (Pandion haliaetus) is a conspicuous large raptor that is valued for wildlife viewing. Ospreys are protected by the Migratory Bird Treaty Act, which prohibits the harming or killing of the species. This provides additional protection when analyzing the effects of a proposed project. The number of active osprey nests is an indicator of the osprey population density in the Tahoe Basin.
- Human disturbance near nesting and foraging areas can impact osprey breeding success. Osprey may be able to habituate to human activity depending on the timing, type, and consistency of the activity. Osprey populations could be limited by the number of large nest trees near water and open areas or competition with bald eagles or other species. However, given the limited number of bald eagles present during the breeding season, and the existing protections for large trees, these are not likely to be major limiting factors in the basin. Osprey that breed in the basin likely migrate to Central or South America for the winter. Osprey breeding in the basin may be affected by a variety of factors in their wintering areas or along migration routes, including contamination from organochlorines (e.g. DDT), which is still used in parts of their wintering grounds.
Example EIP Projects
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Emerald Bay SP UC Davis Osprey Spatial Data Analysis
CA State Parks and UC Davis analyzed 30 years of osprey nesting data to look at reproductive success in relation to distance from potential disturbance factors (roads, trails, etc.).
Monitoring Programs
- The status was based on the number of active nests in the most recent year monitoring was completed. 29 active nests were present in 2019, 725% of the target. Therefore, the current status is considerably better than target.
- Trend was determined using simple linear regression for all years of monitoring data. From 1997-2019, there has been an annual 10.5% growth in the osprey population. Therefore, the trend is determined to be rapid improvement.
- High. Monitoring was conducted using widely accepted protocols and all potential nesting areas are surveyed.
- Medium. Monitoring was conducted using widely accepted protocols and all potential nesting areas are surveyed. Additionally, several years of high-quality data exist. However, monitoring data in the early years is not as reliable.
- Medium.
No photos available.
No documents available.