Lago Los Osos, Quarry Lakes Regional Recreation Area
Grebe Survey Summary
- Max Adults: 16
- Year: 2006
- Most Recent Adults: 2
- Year: 2008
- Survey Type: Shore
- Most Common Threats Reported: Water level too low; lack of nesting habitat; egg predation; lack of fish food; nest parasitism by other grebes; other threats unknown or unspecified
- Lake name:
- Lago Los Osos, Quarry Lakes Regional Recreation Area
- Location:
- California
- Latitude:
- 37.569301
- Longitude:
- -121.9966640
- Surface area (km2):
- 1.22
- Basin type:
- reservoir
- Motor restrictions:
- partial
- Motor restrictions notes:
- no gas-powered
- Management agency:
- East Bay Regional Park District; Alameda County Water District
- Lake use:
- recreation fishing
- Designations:
- Recreation Area
- Comments:
- Part of Quarry Lakes Regional Recreation Area.
Surveys (1)
Survey Citation:
Riensche, D. L., J. D. Mena, and A. B. Shawen. 2009. Western and Clark's Grebe nest platforms designed for fluctuating water levels. Transactions of the Western Section of the Wildlife Society 45: 7-16.
-
Type
shore -
Time period
1990s, August 2008 -
Source
Article -
Both Western and Clarks?
Y
| Count Type | Range | Max | Year |
|---|---|---|---|
| Max Adults | 1 to 100 | 16 | 2006 |
| Most Recent Adults | 1 to 100 | 2 | 2008 |
| Max Nests | 1 to 100 | 6 | 2006 |
| Most Recent Nests | 1 to 100 | 1 | 2008 |
| Max Chicks | 1 to 100 | 31 | 2006 - 2007 |
| Most Recent Chicks | 1 to 100 | 31 | 2006 - 2007 |
Comments:
Historical nesting site of Western and Clark's grebes in the 1990s, entered as present in the 1990s. Artificial nesting platforms were deployed at this lake. Breeding and nesting pair numbers declined over 2006 to 2008. Low numbers in 2008 lumped as present. There were 11 successful nests on these platforms from 2006 to 2008. For 2006 and 2007, 31 chicks were produced at a rate of 1.41(??) but no chick counts per year nor for 2008. For the 3 years of the study, there was an average of 73% nesting success and 60% hatching success rate (not sure what the difference is here). Says the population estimate is 8 pairs (16), the maximum number of nests observed (2006). However, 11 pairs (22) total had successful nests on these artificial nest platforms in 2006 - 2007 combined. Doubled nest numbers per year for adult estimates. Article warns not to use these estimates as an actual census. Lack of prey fish in 2008 attributed to poor productivity that year.