While some people are worried about birds disappearing from their feeders, others continue to be plagued by ravenous grackles and White-winged Doves. It's a device you can make yourself, though it does require some basic woodworking skills. Basically, the roll bar is a dowel mounted lengthwise on the feeder.
Small birds have little trouble getting around it to feed.
We're not making any guarantees, but you might want to give this a try. Banner Golden-cheeked Warbler photo copyright 1988 Greg Lasley. All rights reserved. Travis Audubon Society. All rights reserved.