Hi Carma and everyone else,
I think you're right that it's a Western Wood-Pewee and your "whistling buzzy song" description is spot on for their song. Pewees look more like Olive-sided Flycatchers than any of our other birds. The pewees are much, much more common than the Olive-sided and sound very different. You mentioned the Ruby-crowned Kinglet but of course there aren't any around here in the summer. The kinglet's doppelganger, the Hutton's Vireo, is around in the summer and could be confused with a pewee at a glance. The pewee is slender, has a long tail and only the slightest hint of a wing bar, while the pudgy Hutton's Vireo has a short tail, an obvious pair of white wing bars and a clear eye ring. Hutton's Vireos are uncommon while Western Wood-Pewees are numerous in lowland forests, open woods, meadow edges, parks and some suburbs.
Western Wood-Pewees are entertaining. They
sport a short crest which may flattened depending on their mood.
They are very perky, energetic and can be seen perched in an almost vertical posture on exposed branches, snags, or other conspicuous perches. They snap their heads around as they track flying insects through the air and make short sallies to catch them in mid air and often return to the same perch or nearby. They are mischievous and cranky sometimes. They readily chase one another around, and if there's not another pewee nearby to bother, they may target other species innocently going about their business.
-Don Boucher