Casitas Reservoir/Lake Casitas

Survey Citation:
Robison, K., R. Weems, and D. Anderson. 2008. Western and Clark's Grebe conservation and management in California. Annual report for year four (2008). Report for American Trader and Kure/ Stuyvesant Trustee Councils and National Fish and Wildlife Foundation, California.

• Type
  shore
• Time period
  2008
• Source
  Report
• Both Western and Clarks?
  Y

Count Type	Range	Max	Year
Max Adults	>1000	1000	2008
Most Recent Adults	501 to 1000	1000	2008
Max Nests	1 to 100	<=5	2008
Most Recent Nests	1 to 100	<=5	2008
Max Chicks	1 to 100	1	2008
Most Recent Chicks	1 to 100	1	2008

Comments:

Data from Table 3. Date of surveys not provided. Productivity rate from # of adults in sample and # of young in sample. Estimated total # of adults is entered here. There were reports of "hundreds of chicks in recent years" (Weinerth, Park Services Officer, Casitas Reservoir, pers. comm.). No other information provided. Subsequent reports have their own entries.

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?
  N/A

Count Type	Range	Max	Year
Max Adults	1 to 100	presence?	2013
Most Recent Adults	1 to 100	presence?	2013
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 Lake Casitas, no grebe eggs were collected in 2013 (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.

• Time period
  1994
• Source
  Conservation Assessment, Management Plan
• Both Western and Clarks?
  N/A

Count Type	Range	Max	Year
Max Adults	1 to 100	presence	1994
Most Recent Adults	1 to 100	presence	1994
Max Nests	1 to 100	presence	1994
Most Recent Nests	1 to 100	presence	1994
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 small numbers of breeding grebes and noted as colony site in Lake Casitas, no numbers, years, or other details, assuming 1994 due to source year. Source is Small 1994.