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Home Land Upland Species and Communities

Northern Goshawk

Status and Trend

Interpretation and Commentary

NORTHERN GOSHAWK


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Status: Somewhat Worse than Target
Trend: Little or No Change
Confidence: Moderate

 

  • Relevance - The Northern Goshawk (Accipiter gentilis) is particularly sensitive to human disturbances or habitat alterations because it is a top predator, requires large areas and old growth forest, and has low breeding densities (Squires and Kennedy 2006). 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 stability of the goshawk population in the Tahoe Basin.
  • Adopted Standards  - Maintain 12 Northern Goshawk population sites.
  • Indicator - The total number of reproductively active goshawk territories recorded each year.
  • Status – Over the past 14 years (1997 – 2010) the Threshold Standard of 12 population sites, defined as reproductively active territories, has not been met and the Threshold Standard is not in attainment. The average number of reproductively active territories over the last 14 years and over the 5 years since the last evaluation was 5.7 and 5, respectively, or approximately 45% of the Threshold Standard. The peaks of the previous two cyclical changes in numbers of goshawk nests were near the Threshold Standard. Overall, the indicator is slightly below the standard when the Threshold Standard is interpreted in this way. If the Threshold Standard were interpreted to simply protect 12 sites, the Region would be determined to be considerably better than target because more than 30 territories have been mapped since the adopted Threshold Standard and have been managed according to protective measures outlined in the TRPA Regional Plan.
  • Trend – Over the long-term (1997 – 2010), the number of reproductively active territories has varied between 2 and 11/year. The long-term trend appears to exhibit cyclical variations, although this cyclical trend could be partially influenced by changes in survey effort. The peak of observed cycles appears to have increased to near the Threshold Standard over the time period for which data exists. However, the low point of the cycles has appeared to decrease over the same time period, indicating greater variability in the abundance of goshawk nests rather than an increasing or decreasing trend. The trend in the number of sites protected has increased cumulatively since the Threshold Standard was adopted in 1982.

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  • Confidence  -  There is a high degree of confidence in the quality of the data collected. However, data was often collected to assess the potential impacts of specific proposed projects rather than to evaluate regional status and trends. This reduces confidence in evaluating the indicator status relative to the Threshold Standard with the available information. In 2009, a ten-year goshawk population monitoring effort was initiated that, if fully funded, will improve the future confidence in interpreting regional status and trends (Slauson and Zielinski 2008).Given the variability of the data and the short time period of the data relative to length of each cyclical fluctuation in nest numbers, there is only a moderate level of confidence in the lack of trend. Therefore, there is a medium level of confidence in the status and trend.
     
    Interim Target – Achieve Threshold Standard of 12 population sites (reproductively active territories) during the peak of the next cyclical increase in the number of goshawk nests.
  • Human and Environmental Drivers -  Goshawk populations can exhibit cyclical changes in reproductive success in response to changes in the abundance of prey populations (Doyle and Smith 1994; Salafsky et al. 2005; Wiens et al. 2006). In the Tahoe area, goshawk reproduction can vary in response to weather and pine cone production, which provides food for prey species (Keane et al. 2006). Goshawks are also dependent on old growth forest types. These habitats can be impacted by forestry activities, large fires, and roads and other human activities (Squires and Kennedy 2006; Morrison et al. 2011).
  • Monitoring Approach – Data are collected by the US Forest Service, CA Department of Parks and Recreation, and NV Department of Wildlife following well-accepted protocols. These data are augmented by reports from private or non-profit organizations and qualified individuals (USDA 2009e; USDA 2011d).
  • Monitoring Partners – US Forest Service, CA Department of Parks and Recreation, NV Department of Wildlife, and numerous volunteers and cooperating organizations.

Links

 
  • Monitoring Plan
  • Conceptual Model

Map

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Approximate locations of known reproductively active Northern Goshawk territories from 2006 to 2010. Source: US Forest Service- LTBMU

 

Trend Charts

Chart data not available at this time.
 

Additional Info

References

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Additional Information

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  3. Conceptual Model:
  4. Monitoring Plan:
Last Updated on Wednesday, 05 September 2012 10:15