In addition to the 18 species of warblers that Wallace posted from Rock
Creek this morning, you can add the following:

Hains Pt:
Northern Waterthrush

Kenilworth Aquatic Gardens:
Prothonotary Warbler (quite vocal and active over the ponds)
Yellow-breasted Chat (heard at end of boardwalk from Kenilworth Park)
Hooded Warbler (at the entrance to the Gardens)

That brings the cumulative list up to 22.  Did anyone pick up a Pine at the
Arb or Louisiana Waterthrush in Rock Creek?  Either way, not too bad for
late May in DC.

Good birding,
Paul Pisano
Arlington, VA