If they vanished for the same reason they vanished around here, it had nothing to do with the change in feed.
The Feds poisoned the starlings here. In the end they got a little too aggressive and got some Grackles too.
Quite a day.
American Goldfinch
American Redstart
American Robin (3 different juveniles)
Eastern Kingbird (family of three)
Gray Catbirds
Least Flycatcher
Swainson's Thrush
Western Tanager
Yellow Warbler
These are in addition to the regulars.