Saturday there was a Merlin at the top of the tallest tree in the NE corner of Montrose Park (north or R St between 30th & 31st Sts NW).  I've seen it in the same spot at least 2 previous winters, eating its lunch.  
 
Montrose also typically has a good number of Towhees, maybe a Winter Wren or 2 (both more likely down the hillside toward Dumbarton Oaks Park), various woodpeckers, and sometimes an interesting sparrow, buteo or accipiter.  Red-shoulder Hawks and Barred Owls have nested in Dumbarton Oaks Park (behind Montrose) in recent years.
 
If you want go looking for the Merlin, start from the park entrance nearest 30th St, head straight back past the restrooms on your right, open area, then playground on your left.  There's a backstop in the NE corner before the park slopes down toward Rock Creek, and about the 3rd tree S of that backstop, along the E edge of the park, is taller than the other trees around it.  That seems to be the Merlin's favorite spot.

Carrol Cowan