Comments on the song of the Blackburnian Warbler: 

Stokes, "Song is a series of thin high-pitched notes with last note very high, like "tsip, tsip, tskip, titi, tzeeeee."  Call is a nonmusical "tick".  

Robbins:  "Song is very high and thin, often with an exceedingly high-pitched ending, 4-6/min."

Peterson:  "The most distinctive song begins with several well-measured "zip" notes on the same pitch and ends on an extremely high thin slurred note: "zip, zip, zip, zip, tti tseeeeee."  This wiry end note is diagnostic if your ears can catch it.  Another song is more like Nashville's, a two-parted affair: "tizip tizip tizip, tizip, zizizizizizizizi."

Related site on Blackburnian Warbler: http://www.mbr.nbs.gov/id/framlst/i6620id.html (Patuxent), field identification, song,  photos, migration, distribution, taxonomy.

Smithsonian Migratory Bird Center, http://www.si.edu/smbc/bom/blwa.htm.