Last night (10 May into 11 May), weather conditions were very favorable for migration south of Iowa. Central Iowa had a pretty strong east wind at the surface up to about 2000 feet. The "donut" signature on radar indicates birds continued to migrate northward into central Iowa at altitude. Radar showed little migration below 2000 feet, but moderate migration at 3-5000 feet. The radar "beam" increases in altitude the farther one gets from the radar, so it samples different elevations and different ranges. Quite interesting. As the night went on, the donut filled in, possibly as birds descended to land.
As the rain ended here south of Boone about 830 am and the east wind blew, we had a storm of orioles around our feeders and yard. Five male Orchard Orioles (FOY here) and at least 8 bright male Baltimore Orioles were fussing with a half dozen or more first year female Baltimore Orioles and a handful of other females. 20 minutes later, activity was back to more normal levels!