I am glad someone else saw a Coopers in DC, so I don't feel so strange
about seeing them. About 2 weeks ago, early in the morning, there were 2
Coopers, possibly involved in mating behaviour, around 411 D ST NW.

Subject: [MDOSPREY] Another Wacky City Hawk

Walking home at 6:20 near the corner of 14th and E. street SE (two
blocks up from the Potomac Metro stop) I watched a COOPERS HAWK perch
on a branch over the road before flying off toward 15th Street. 
Although it looked small for a Coopers, its rounded tail was clearly
visible as it flew overhead.