In response to Richard Woods' question regarding safe dates:

Safe dates define the early and late dates which determine whether a bird 
seen in a given area could be considered a "Possible Breeder" or not.  
Outside of the safe dates, the bird could still be a migrant passing 
through.

For full details on the Breeding Bird Atlas procedures, check out the 
Atlas website at:

http://www.mdbirds.org/atlas.html

Click on the "Handbook" tab for the safe dates for all known Maryland 
breeding species.

Norm
Colesville & West Ocean City, MD