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Home Land Upland Species and Communities

Nesting Bald Eagle

Status and Trend

Interpretation and Commentary

NESTING BALD EAGLE


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Status: At or Somewhat Better Than Target
Trend: Little or No Change
Confidence: High

 

  • Relevance - The Bald Eagle (Haliaeetus leucocephalus) is the national symbol and an iconic species that is exceptionally important to the public. In the lower 48 states, Bald Eagles were considered threatened under the Endangered Species Act until they were de-listed in 2007. They are still protected by the federal Bald and Golden Eagle Protection Act and Migratory Bird Treaty Act, which prohibit the harming, killing or possession of Bald Eagles, or their eggs or nests. The number of nests that successfully produced at least one juvenile is an indicator of the Threshold Standard of one nesting population site.
  • Adopted Standards  - Provide a minimum of 1 population site and a 0.5 mile disturbance zone around population sites
  • Indicator - The number of nesting Bald Eagle pairs that successfully fledged at least one juvenile each year.
  • Status – Over the past 15 years (1996-2010), the number of reproductively successful nests, has met or exceeded the Threshold Standard of one population site 9 times, or 60% of the time. Over the past 5 years (2006-2010), the Threshold Standard has been met 4 times or 80% of the time. In general, one pair of Bald Eagles consistently nests in the Tahoe Basin, although in 2000, a second pair was present and successfully reproduced. Therefore, the indicator is “at or somewhat better than the target” or in attainment with the Threshold Standard. Three mapped areas have been identified by TRPA for the protection of the nesting Bald Eagle population (see map below).
  • Trend –  Since 1996, the number of reproductively successful nests has fluctuated between 0 and 2. As described above, one nesting pair has been present in most years. The lack of variation in the data, and the consistency with which one nesting pair has been observed, clearly indicate that there is no increasing or decreasing trend.

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  • Confidence  - There is a high degree of confidence in the status because all known nests are intensively monitored by qualified wildlife biologists. In addition, eagle nests are relatively easy to find, and formal boat surveys are conducted monthly during non-winter months to identify any new nests. The high confidence in the quality of the data combined with the lack of variability in that data provide a high level of confidence in the trend.
  • Human and Environmental Drivers - Bald Eagle reproductive success in the Tahoe Basin may be affected by human activity such as boat access or other recreational uses in nesting territories (Romsos 2000a), and the loss of nesting habitat including large trees in close proximity to surface water (Romsos 2000a; USFWS 1986). However, these impacts are minimized by TRPA’s enforcementof disturbance buffers surrounding nest sites. The amount of fish mortality from spawning, disease, or catch and release fishing can control the amount of available carrion, which can affect nesting Bald Eagles (Jackman et al. 2007; Beauchamp et al. 1994). In other areas, weather conditionshave been shown to affect reproductive success (Gende et al. 1997), although it’s unknown to what degree weather affects nesting success in Tahoe.
  • Monitoring Approach – Known nest sites are regularly observed during the incubation and fledging periods to determine reproductive success. Monthly boat surveys are conducted during non-winter months to identify any new nest sites surrounding Lake Tahoe, and ad-hoc surveys are conducted in other areas in support of environmental assessments for proposed projects.
  • Monitoring Partners – California Department of Parks and Recreation, Nevada Department of Wildlife, U.S. Forest Service.

Links

 
  • Monitoring Plan
  • Conceptual Model

Map

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Approximate locations of known Bald Eagle nesting areas from 1996 to 2010. Source: USFS and TRPA Survey Records

 

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 Tuesday, 04 September 2012 12:39