Lower Otay Reservoir/Lower Otay Lake

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?	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 Lower Otay Reservoir, 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:
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	101 to 500	250	2008
Most Recent Adults	101 to 500	250	2008
Max Nests	1 to 100	10	2008
Most Recent Nests	1 to 100	10	2008
Max Chicks	1 to 100	4	2008
Most Recent Chicks	1 to 100	4	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. Water ski courses in the lake. No other information provided. Subsequent reports have their own entries.

Survey Citation:
Unitt, P. 2004. San Diego County Bird Atlas. In Proceedings of the San Diego Society of Natural History, 39:i–vii, 1–639. Available: http://sdplantatlas.org/BirdAtlas/BirdPages.aspx.

• Time period
  1999, 2000
• Source
  Website
• Both Western and Clarks?
  Y

Count Type	Range	Max	Year
Max Adults	101 to 500	150	2000
Most Recent Adults	1 to 100	55	2001
Max Nests	1 to 100	presence	1999-2001
Most Recent Nests	1 to 100	presence	1999-2001
Max Chicks	1 to 100	presence	1999
Most Recent Chicks	1 to 100	presence	1999

Comments:

Species account of Western and Clark's breeding in San Diego County. Described as large colony at this lake with Western grebe count including chicks in 1999 and 2000 (uncertain if chicks included) and Clark's grebe adults counted in 2001. Most likely both Western and Clark's grebes were present in all those years. Western grebes in 1999 observed by V. Marquez, Clark's grebe broods in 1999 observed by S. Buchanan who also observed Western grebes in 2000.