There is a good description of Steller's Jay courtship song, typically performed by males within a dense bush, at Birds of North America Online. Likely what you heard. Infrequently heard in my experience.

Bob Sundstrom

Sent from my iPhone

> On Mar 4, 2015, at 10:18 AM, Joshua Glant <josh.n.glant at gmail.com> wrote:
>
> Hello Tweets,
>
> While walking down a neighborhood street yesterday afternoon, I heard the strangest bird call coming from a 4-foot tall rhododendron bush in a yard. It started with the cluck-cluck-cluck of a Yellow-billed Cuckoo, then switched to a Song Sparrow-like warbling that made me wonder if an exotic Asian finch hadn't escaped from some nearby aviary or cage. I proceeded to record the sound, and I leaned down to peek into the bush and try to spot the singer.
>
> I walked closer and closer, inching slowly forward so as not to scare it. The bird cuckoo-clucked again, then warbled once more. Suddenly and without warning, a Steller's Jay, blue-black plumage, crest and all, came shooting out of the bush and flapped rapidly away with an annoyed chatter.
>
> Half an hour later, I heard the same sound again, and looked up to find a (the) Steller's Jay perched atop a cedar.
>
> I have never heard anything like it. It reminded me of the Raven's "comfort sounds", softly given to a mate or chick, who can also make the sound as well.
>
> I felt like I had walked in on someone who was humming to their self in a quiet room!
>
> Also, I heard a Band-tailed Pigeon screech and then coo at Ellis Pond. A single call note that sounded exactly like a Western Tanager got adrenaline rushing for a moment, as I had just been reflecting on the one that I had seen there last August and then another in my yard a week later. And the House Finches are very numerous in the area around the pond, even though they are scarce at my house just on the other side of the woods!
>
> I spent a while trying to find ways to recognize individual Mallards at Ellis Pond.
> The male with heavily brown-flecked sides is my favorite, and he sticks constantly with his mate, the one with the gray-green bill. The dominant male had the whitest flanks, and his quacks would almost always get a response. There was one hen with a bright orange bill, another drake with brown streaks on the sides, and then there were about 7 other Mallards also there, enjoying a few scraps of bread thrown by neighbors and kids.
>
> On a final note, "Barry" the Barred Owl (though there's a good chance that there is more than one in our neighborhood) was hooting quite loudly and quite close to my window last night. Instead of the normal 8-note pattern, (s)he called in a string of the same note, like "who-cooks-cooks-cooks-cooks-cooks-for-you-all?", giving the effect of an object spinning rapidly as it whooshes through the air.
>
> Beautiful and birdy as always in this early spring! Let's hope the wintering birds hang around for a bit longer, otherwise mid to late March may be a bit slow for birders.
>
> Good birding, Joshua Glant
>
> Mercer Island, WA
>
> Josh.n.glant at gmail.com
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