Use eBird to document the peak of spring migration! It also coincides with the International Migratory Bird Day. See details at the website of the Pennsylvania Society for Ornithology, which notes:
Held on the second Saturday in May, this event is similar to the Christmas Bird Count except it is done on a county basis, rather than a 15-mile diameter circle. Participants go out and identify and count all of the birds they can find on that day (including owling at night if so inclined).
Click through to find the name and contact information for the compiler in your county.