A pair of Common Ravens are nesting in Cabin John (Montgomery County; the part of Cabin John along MacArthur Blvd) - which explains the sightings of a pair of this species a couple of months back.  They have constructed a nest on the water tower that has at least 2 chicks in it.  You can't see the nest well if you go close to the tower's compound (the nest is around 120 ft or more up in the air anyway) - it is best viewed from the other side of Seven Locks Rd.  I don't believe these birds were here in previous years.

Good birding

Clive Harris
Cabin John, MD