Some confusion over different birds seen apart by several birders Independently but based on more photos received from Klemens Gasser the original finder along with Will Pollard points to CLAY COLORED SPARROW.
Latest Pictures showed brown rump and a white median head stripe characteristic for this rare spizella species. ( Chippings is gray rumped and gray median)
The bird was first found on the slope lawn below the Maryland Monument then across the road in tree along the snow fence line of the Peninsula..
Good one by Klemens and group. If it makes it at least to Wednesday for Xmas count week, its in.