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O'Neill Forebay

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Grebe Survey Summary

  • Max Adults: 15 (2007), presence (other years)
  • Year: 1990s, 2003?, 2013, 2007
  • Most Recent Adults: presence?
  • Year: 2013
  • Survey Type: Shore; Boat; Air
  • Most Common Threats Reported: Water quality/contaminants
Lake name:
O'Neill Forebay
Location:
California
HydroLAKE ID:
112726
GRanD ID:
225
Latitude:
37.09375
Longitude:
-121.047917
Surface area (km2):
8.7
Basin type:
reservoir
Dam completion date:
1966
Management agency:
California Department of Fish and Wildlife; U.S. Bureau of Reclamation
Lake use:
hydroelectric
Region associations:
Central Valley Project; San Luis Joint Use Project; O'Neill Forebay Wildlife Area

Surveys (2)

Survey Citation:
Ackerman, J. T., C. A. Hartman, C. A. Eagles-Smith, M. P. Herzog, J. Davis, G. Ichikawa, and A. Bonnema. 2015. Estimating mercury exposure of piscivorous birds and sport fish using prey fish monitoring. Environmental Science & Technology 49:13596–13604.

  • Type
    boat
  • Time period
    April 2012, October 2013
  • Source
    Peer-reviewed
  • Both Western and Clarks?
    Y
Count Type Range Max Year
Max Adults 1 to 100 presence? 2012
Most Recent Adults 1 to 100 presence? 2012
Max Nests N/A N/A N/A
Most Recent Nests N/A N/A N/A
Max Chicks N/A N/A N/A
Most Recent Chicks N/A N/A N/A

Comments:

Not a survey but grebes were sampled at 25 lakes in CA from April to October of 2012 (13 lakes) and 2013 (12 lakes). An average of 14 grebes per lake (from 2 to 38 grebes) were captured at night with night-lights. No breakdown of actual numbers captured per lake was provided. Morphometry and molt data, along with blood was collected from each bird for mercury analysis, and sex determination via genetic analysis. From 7 out of the 25 lakes, an average of 14 grebe eggs (from 6 to 23 eggs) were collected. An egg from each randomly sampled nest was collected either from an active nest (random egg) or from an abandoned nest (abandoned egg). Prey fish and sport fish were also sampled an average of 11 days after grebe sampling. At O'Neill Forebay, no grebe eggs were collected in 2012 (Figure SI). 354 grebes were captured total from the 25 lakes, 71% were Western grebes, 29% were Clark's, 48% were female, 52% were male. 101 grebe eggs were collected from 7 lakes, of which 62% were Western grebes, 15% were Clark's grebes, 23% were unidentified which. Grebe blood, eggs, and sport fish mercury concentrations were strongly correlated to mercury concentrations in prey fish at the lakes. Grebe mercury concentrations were also strongly correlated with sport fish mercury concentrations. This study showed that prey fish monitoring can estimate mercury exposure of grebes and other piscivorous birds if these birds can't be sampled directly.

Survey Citation:
Ivey, G. L. 2004. Conservation assessment and management plan for breeding Western and Clark’s Grebes in California. Unpublished technical report. American Trader Trustee Council, California. . Accessed 15 January 2020.

  • Type
    air
  • Time period
    1990s, 2003
  • Source
    Conservation Assessment, Management Plan
  • Both Western and Clarks?
    Y
Count Type Range Max Year
Max Adults 1 to 100 presence 1990s, 2003?
Most Recent Adults 1 to 100 presence 2003?
Max Nests 1 to 100 presence 1990s
Most Recent Nests 1 to 100 presence 1990s
Max Chicks N/A N/A N/A
Most Recent Chicks N/A N/A N/A

Comments:

This entry to capture historical record of breeding grebes in CA prior to 2002. There were breeding grebes and noted as colony site in O'Neill Forebay in the 1990s, no numbers or other details. Source is D. Shuford, pers. comm. On August 5, 2003, an aircraft survyed Central Valley lakes for colonies for which there were recent grebe sightings or possible habitat but no data on what was found, if anything, for this lake.

Sources of Information

  • Messager, M. L., B. Lehner, G. Grill, I. Nedeva, and O. Schmitt. 2016. Estimating the volume and age of water stored in global lakes using a geo-statistical approach. Nature Communications 7:13603. Data is available at www.hydrosheds.org.; Lehner, B., C. Reidy Liermann, C. Revenga, C. Vorosmarty, B. Fekete, P. Crouzet, P. Doll, M. Endejan, K. Frenken, J. Magome, C. Nilsson, J.C. Robertson, R. Rodel, N. Sindorf, and D. Wisser. 2011. Global Reservoir and Dam Database, Version 1 (GRanDv1): Dams, Revision 01. Palisades, New York: NASA Socioeconomic Data and Applications Center (SEDAC).
  • Lehner, B., C. Reidy Liermann, C. Revenga, C. Vorosmarty, B. Fekete, P. Crouzet, P. Doll, M. Endejan, K. Frenken, J. Magome, C. Nilsson, J.C. Robertson, R. Rodel, N. Sindorf, and D. Wisser. 2011. Global Reservoir and Dam Database, Version 1 (GRanDv1): Dams, Revision 01. Palisades, New York: NASA Socioeconomic Data and Applications Center (SEDAC).
  • O’Neill Forebay Wildlife Area
  • O'Neill Dam and Forebay Information
  • O'Neill Dam
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