So thanks to all who assisted in this adventure and sent a variety
of photos. What does one do when seeing an apparent Dusky
Thrush in the park & not make a complete fool of one's self?

Take the white head off of a leucistic Varied Thrush. Remove
a black breast band from another Varied Thrush. Splurge
lots of rusty orange color from an actual Varied Thrush around.
Finally take a black eye stripe from a real Dusky Thrush. Mix
it all up and bingo there you have it - a Harlequin Thrush, in
actuality a lurid leucistic Varied Thrush ( I think !) It was a lot of
fun while it lasted.

Best to all, David Hutchinson