Mystery bird

Yesterday at Maplewood Flats, North Vancouver, occupied Coast Salish territories, a brown bird was fluttering in a tree and eating blossoms when it dropped this song. Can you help me return it to him? Mystery bird by Blacksquirrel

Mystery bird was brown, with a heavily streaked breast, a moderately thick beak (sparrow/finch-like), a long, slender, notched tail, house finch-like. Size of a large sparrow, bit smaller than a thrush. Feeding in a tree, then in bramble thicket. Very active, bursting into song in the middle of a mouthful and dropping the flower it had just plucked! Any ideas?

Update
It has been suggested by a more knowledgeable birder than myself that this might be a Purple Finch imitating a Swainson's Thrush. It does sound like a cross between the Purple Finch's song and the Swainson's Thrush's! However if it was a Purple Finch, then it wasn't an adult male, because it didn't have any colour apart from brown and whitish. Also I've heard it (though not seen it) both times I've been back to Maplewood Flats since I made the recording. So would an immature male be practicing his vocals by very consistently and repeatedly borrowing another bird's song? It might enable him to avoid the ire of territorial males... Though I haven't noticed any other Purple Finches. Also, I haven't noticed any Swainson's Thrushes, so where would a juvenile have learned their song? Surely a year-old finch is no longer a juvenile, right? Or would a female Purple Finch have discovered a musical yearning? There was I assuming only male songbirds sang! Many questions still to be explored...

"The Purple Finch (sober-colored) is a rich singer. As I said the other day, something like a Warbling-Vireo, only louder, clearer, mellower and more various." - Henry David Thoreau


Update 2
The plot thickens as I find out that male Purple Finches take 2 years to get their adult plumage; first year males look like females. So maybe this is a one year-old male who heard the Swainson's Thrush last year and is singing it again this year before the actual Swainson's Thrushes have returned.

The magical song of the Swainson's Thrush is a harbinger of the return of summer and the season of plenty in the Pacific Northwest. In several First Nation languages along the coast of British Columbia it is known as "Salmonberry Bird" because its song rises from the thickets at the same time as the salmonberries start to ripen. In several languages such as Saanich, the song even lists the different colors and kinds of salmonberries (golden, red, dark...).

Would a hungry Purple Finch be trying to hasten the ripening of the berries?