On Monday, Feb. 12, at about midday, there was still a lot of ice in Ellis Bay and the Mississippi due to the mostly cold weather over the past week -- and yet the gull population seemed way down. Both above and below the dam, on both sides of the river, Ring-billed Gulls were in the mid-100's, with correspondingly fewer Herring Gulls. The swirling mass of gulls over the spillway had become much sparser.
Nevertheless, there were still at a least a couple of individuals of the uncommon species. I found one first-cycle Lesser Black-back and one adult Iceland (Thayer's) Gull working back and forth at the spillway. Photos are in my eBird list for that hotspot (Melvin Price Lock and Dam 26).
I noticed in passing that the open pools in Ellis Bay held a number of swans, too, so they certainly aren't all gone.