The Pennsylvania Migration Count (PAMC) details, forms, and reports are available at this PSO webpage

Centre County PAMC data from 1993 through 2011 (except for 1997,  1999, and 2008)

Huntingdon County PAMC data from 1993 through 1999

Both sets of data give a good representation of the species expected to be seen in Centre and Huntingdon counties during mid-May.

Note that according to this article "the PAMC originated as part of the continent-wide North American Migration Count (NAMC) in 1992, when there were 141 observers in 10 Pennsylvania counties. The count grew steadily in popularity in PA over the years, and was renamed PAMC in 2003, reflective of the fact that the national count was struggling everywhere but in Pennsylvania.  In 2010, 704 observers from 40 counties participated in the PAMC."