Do Barred Warblers ever drop there tail like Olivaceous do?

Answer 1

I don't know, but perhaps you may be able to tell from these pictures:

http://www.birdseen.co.uk/photos/photocistic.htm

http://www.surfbirds.com/birds/oldworldwarbsetc.html

You can also use this link to find more info about Olivaceous Warblers, See Site Below:

http://www.birdguides.com/html/vidlib/species/Sylvia_nisoria.htm