Hi Steve,
 I am very familiar with the area where this bird was reported. The SP stands
for Springs Trail, and is (or was) a good area for Kentucky Warbler, Hooded
(occasionally), Louisiana Waterthrush (commonly breeds there, at least a pair),
and Ovenbird, so the habitat is good for a Swainson's Warbler. In fact it is
one of only a couple of places in the park where you could see a bird and
think "Swainson's".  Houses are creeping in to the edge of the park here, and
habitat is beginning to dwindle for these breeders.  You should encourage him to
submit a report to "the committee" anyway, just for the records.

Rick Sussman
Ashton,MD