HI Catherine,

One other species that sounds to me like it's calling suweet? suweet? is the Hutton's Vireo. You can find all of the suggested species' audios on-line at various sites, such as the Cornell Lab of Ornithology:

http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/

Good luck,

Lonnie Somer
Olympia, WA
wheelermombi at comcast.net