I need help identifying a bird by its call. It's a sparrow sized bird and calls from high in conifers, buried in the foliage. I have heard two versions of the call, one in Bellingham and the other in Seattle, although I am convinced they are the same bird. The call is a quick ascending whistle followed by a long clear descending whistle (Bellingham version). The Seattle version's ascending note is so quick it's almost imperceptible but the descending note is identical. This is repeated fairly regularly every few seconds without variation. The bird is solitary and there do not seem to be answering birds around. Also, there was no apparent flight call.
I have looked through my bird books and listened to a Cornell catalog of 250 American birds without success. The closest I came was the Hutton's vireo but the habitat was wrong.
Any ideas?
John Dunne, Bellingham