I counted 251 Western&Clark's Grebe by boating Santa Margarita Lake. Further information is on my eBird Checklist https://ebird.org/checklist/S73284367 or kathannelynch3 AT gmail DOT com.
If you plan to make a special trip to Santa Margarita Lake to see the grebes, contact me first if you'd like to get an idea of how to see what you hope to see. Only 12 nests left in the main bay, and adults will depart within days. All viewing will then be more distant but possible in certain places with binoculars from land or visually by boat.
GREBE COUNT DATA (count by me, not official group):
Western Grebe: 23 adults plus 8 young
Clark's Grebe: 93 adults plus 13 young
Western/Clark's Grebe: 77 adults plus 37 young
TOTAL = 251 Western&Clark's GREBE on Santa Margarita Lake (summed the above 31 Western plus 106 Clark's plus 114 W/C)
NEST DATA By motorboat. Verified 12 active nests by several (boat and land) counts.
NOTE: The ratio of Western: Clark's was 1:3. (yes, meaning three-quarters were Clark's and Westerns were outnumbered by Clark's)