Black-capped Song from Eugene, Oregon. This is one of numerous song-types found west of the Cascades in Oregon and Washington, north to Everett. All these song-types are typical chickadee whistles, but the "hey-sweetie" of the continental populations is absent or very rare in this area. Interestingly, the area in which "hey-sweetie" is not sung is, approximately, the range of one of the subspecies of Black-capped Chickadee, Poecile atricapillus occidentalis called "Oregon Chickadee" by some. According to Susan Smith in The Black-capped Chickadee, (1991, Cornell Univ. Press) the range of this subspecies extends up into southwestern British Columbia, where "hey-sweetie" is sung.
"Continental" form of the Black-capped Chickadee song. Transliterates nicely as "hey-sweetie." "Sweetie" captures the extremely brief break in the second note. Notice the brief indentation in the blue graph of loudness at the top of the figure. Black-capped Chickadees from the Atlantic to the Pacific sing this song-type and no other. The exceptions are in three places: Martha's Vineyard, Mass., Alaska, and west of the Cascades from northwestern Washington south to at least Bandon, OR, and probably south into coastal California. Donald Kroodsma gives an engaging account of his research into this pattern in The Singing Life of Birds (2005, Houghton Mifflin). He says this is the song-type used in eastern Washington and eastern Oregon, but I have been unable to confirm that. I have recorded this song-type near Bellingham, Washington.
A Mountain Chickadee song from Klamath County, central Oregon. Very similar to the song above, by a Black-cap, but notice the distinct break between the final two notes.
A Mountain Chickadee song from central New Mexico, in the Sandia Mountains east of Albuquerque. This dialect has the longest song I know from Mountains, but if you take out the short notes, it is very similar to the one above, from Oregon.