Indicator
Northern Goshawk Population Sites
2023 Evaluation
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This indicator measures the number of active nesting territories of northern goshawk in the Tahoe Region. Goshawks have special designations by TRPA, the states of California and Nevada, and the USDA Forest Service, providing them with increased levels of protection. The species is a top predator, requires large areas of mature to old-growth forest with multiple stories and a high canopy cover, and has low breeding densities. The northern goshawk is particularly sensitive to human disturbance and habitat alteration. Regional programs such as protecting old-growth forests and limiting recreation around known nesting areas aim to increase the northern goshawk population. Monitoring is conducted by partner agencies mostly using acoustical surveys. 

In 2023, the American Ornithological Society reclassified the Northern Goshawk, which was found in both North America and Eurasia, into two distinct species: the American Goshawk and the Eurasian Goshawk. The Northern Goshawk has been renamed the American Goshawk (Astur atricapillus).

Northern Goshawk Population Sites - photo by Paul Williams.jpg
Status

Number of reproductively active American goshawk territories recorded during surveys in the Lake Tahoe Basin (1997 to 2023). The threshold standard is 12 population sites. Survey effort varies considerably each year complicating status and trend determinations.

Data provided by the U.S. Forest Service. Access detailed datasets on Tahoe Open Data, including: Goshawk Habitat Data and Annual Data.

2023 Evaluation
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Status
Insufficient Data to Determine Status or No Target Established
Trend
Insufficient Data to Determine Trend
Confidence
Not available
Applicable Standard
W1: Provide a minimum of 12 Goshawk population sites. W8: Provide disturbance zones in the most suitable 500 acres surrounding nest site including a 0.25 mile buffer centered on nest sites, and influence zones in 3.5 mi for Goshawk.
Key Points
  • The USDA Forest Service monitors for goshawks in advance of fuel reduction projects. The current survey effort for american goshawks is opportunistic and was not developed to assess or estimate population size or status, so the current population status is unknown.
  • Monitoring of american goshawk populations have fluctuated signficantly over time, ranging from intensive to minimal, largely driven by budgetary and staffing constraints. As a result, reliable estimates of population trends are unavailable.
  • Based on the number of active territories observed in a partial survey of the Tahoe Region in 2019, a more comprehensive survey might reveal more active territories, meeting or exceeding the TRPA threshold standard of 12 active nesting territories. 
  • More than 30 territories have been mapped throughout the Tahoe Region. The TRPA, in collaboration with partner agencies, has implemented a disturbance zone standard to protect these sites. 
Evaluation Map
Description

Approximate locations of known reproductively active northern goshawk nest sites from 2006 to 2023 within the Tahoe Region.

About the Threshold

The American goshawk (Astur atricapillus) is particularly sensitive to human disturbance and habitat alteration. The species is a top predator, requires large areas of mature to old-growth forest with multiple stories and a high canopy cover, and has low breeding densities. Goshawks have special designations by TRPA, the states of California and Nevada, and the U.S. Forest Service, providing them with increased levels of protection. The number of reproductively active territories is an indicator of the health of the northern goshawk population in the Tahoe Basin.

American goshawk populations can exhibit cyclical changes in reproductive success in response to changes in the abundance of prey populations. American goshawk reproduction can vary in response to weather and pine cone production, which provides food for prey species. American goshawks are also dependent on mature to old-growth forest types. American goshawk habitat suitability can also be impacted by forestry activities, large fires, roads, and other human activities.

Delivering and Measuring Success

EIP Action Priorities

Example EIP Projects

Monitoring Programs

Rationale Details
Insufficient Data to Determine Status. Monitoring efforts for the species are primarily aimed at mitigating project impacts (threshold implementation), rather than assessing the overall regional population (threshold assessment). Survey effort and spatial coverage vary considerably from year to year, largely influenced by the geographic location of proposed forest health treatments. The most recent regional population survey, conducted over a decade ago, documented 10 active nests, compared to the threshold standard target of 12. The current population status relative to the threshold remains unknown.
Insufficient Data to Determine Trend. Population trend analysis has not been conducted due to inconsistent monitoring efforts over the years, which have primarily focused on assessing project-level impacts rather than comprehensive population monitoring. This inconsistency in data collection undermines the reliability of population assessments, as it prevents the establishment of a robust dataset necessary for detecting meaningful population trends.
Confidence Details
N/A. A full population survey has not been conducted in over 10 years. Monitoring has been focused on project impacts.
N/A. Monitoring effort has varied widely through the years.
N/A
Additional Figures and Resources

No photos available.

No documents available.