2 males and 1 female were swimming on a large pond on private property, visible from the eastern edge of Foothill Regional Park along Oakwood Trail. The third picture shows the pond.
I first found this Anna's Hummingbird nest on March 29 when I heard the female buzz above my head and then saw it fly up to sit on a nest in a leafless blue(?) oak. At some point, the female left and later returned with a small feather, which it quickly worked into the rim of the nest. On April 7, the female was sitting on the nest when I first arrived. She came and went a few times. I believe she sat on the nest for awhile each time she visited, but I didn't record the details in my notebook. One time she seemed to be working something into the rim of the nest. When I arrived on April 12, the female was again sitting on the nest. She left a few times and returned. She was either working something into the nest (I didn’t see her bring in any nest material) or feeding very small young. I suspected the latter. It had been raining in recent days so it would make sense if she was brooding the young in between feedings. I checked the nest again on May 2, but it looked like the nest had been predated. The feathers in the cup were visible and looked like they had been loosened.
The nest was covered in lichen and expertly camouflaged. It looked very similar to another Anna's Hummingbird nest that I found in an oak last year. The nest was on a limb overhanging Westside Trail.
The first two pictures were taken on April 12, and the other two were taken on April 7. The last picture shows the nest-site; the nest is circled in red.
My husband and I did a 1-night backpacking trip at Lake Sonoma and camped at Old Sawmill Camp on the Warm Springs Arm. On the morning of April 22, 2012, I heard a strange guttural croaking call coming from the lake so I went down to check it out. I was excited to find a male Hooded Merganser floating on the lake. It soon took off and flew up the lake. Two female mergansers then flew into the area and landed, but I am fairly certain they were Common Mergansers.
The call that I heard sounded just like the "male display" call that's available on the Hooded Merganser page for Cornell's All About Birds (http://www.allaboutbirds.org/guide/Hooded_Merganser/sounds). The call is described as the "craaa-crrrooooo" call in Birds of North America online (although I don't think that's a very good description; it sounded more like "be-boooooow" (as in bow-wow) to me, but it's the same call (I listened to the "craaa-crrrooooo" audio associated with the BNA account)). Birds of North America says that Hooded Mergansers are "typically silent. Vocalizations most commonly heard during courtship and around nest sites. Male produces a rolling frog-like craaa-crrrooooo." BNA also mentions a hollow pop, which I heard as well.
I wonder if this Hooded Merganser was thinking about nesting in Sonoma County; or it may have just been starting courtship behavior before arriving on its nesting grounds. The habitat around Old Sawmill Camp is definitely suitable, but as far as I know (and I've talked to someone who's pretty knowledgeable about these things), there are no breeding records for Hooded Mergansers in Sonoma County. Old Sawmill Camp is near the upper end of the Warm Springs Arm and the lake is pretty narrow there (<50m across). The lake was full at the time.