As Iowans consider trading their lawn mowers for snow blowers in the garage, they’re also setting bird feeders in the yard for the approaching winter. While most Iowa bird watchers want to -attract- the feathered creatures, one expert says it’s a challenge to keep some “playground bully” birds away.Iowa Department of Natural Resources spokesman Joe Wilkinson says the “undesirables” like blue jays or grackles often drive away other species of birds. He says you might discourage them by keeping the feeder empty for a few days.Wilkinson says bird feeding is Iowa’s number one outdoor recreation during the wintertime, especially since it lets you to enjoy the outdoors -from- the indoors. He says it’s an inexpensive hobby which can be started with a simple birdfeeder and the right choice of seed.He says by stocking feeders now, Iowans can make their yards a regular stop as the winter migration gets underway.