I am not sure exactly what time this was recorded except to note that it was made between 11 PM and prior to the start of the "dawn chorus."  No way to tell if this call was made in flight or from a perched location.  Habitat around my house is not conducive for Acadian Flycatchers.  I have had Eastern Wood-pewee pass through my yard during the day in Spring migration and a "traill's" type flycatcher pass through in the Fall.  *2007 update - I recorded another Acadian Flycatcher "pseet-seeup" call on 5/5/07.