As suddenly as they came, they were gone, off down the street to the next stop in someone else's tree.
Bushtits are the smallest songbirds in North America (by weight) -- the smallest of any birds on the continent except hummingbirds. Even my resident chickadees look big beside them. According to Cornell Lab of Ornithology's "All About Birds" site (http://www.allaboutbirds.org/guide/Bushtit/lifehistory) the range from 2.8 to 3.1 inches and weigh between one and two tenths of an ounce. (By contrast, the Anna's hummingbird, common in this area, averages about 3.9 inches and weighs almost the same.) They also note that the Bushtit is the only member of its family found in North America -- there are seven others species across Eurasia -- and they build complex, hanging nests. My favorite field guide, "Birds of the Puget Sound Region" (by Bob Morse, Tom Aversa and Hal Opperman) describes an " ... extraordinary hanging nest woven of moss, lichen, spider web and other material, up to a foot long with small entrance near top, usually less than ten feet from the ground." I've never seen one of these nests in person, but I would love to.
Bushtits were one of the first species discovered to have "helpers" at the nest. Extra individuals, presumably related, who help the mother and father with care of the young. All the family members (again, according to "All About Birds") sleep together in the nest, but they leave it after the chicks fledge.
My own experience with Bushtits is limited to these sudden visitations in my yard, two or three times in the last eight months. I knew absolutely nothing about them before those encounters. Unlike the chickadees and juncos who spend so much time in my yard and at my feeders, the Bushtits come and go very quickly. It might take a lot longer to really get to know them.