The University of Illinois, FAA Center of Excellence for Airport Technology (CEAT) has initiated validation studies at all of its radar installations. The studies vary by location including different types of observations based on the location specifics. CEAT participated in the IVAR studies with SPAWAR and other agencies which utilized avaian radar systems provided by ARTI. Based on these experiences, CEAT initiated this study using field observations of bird movements and specific bird targets over a 15 month period to evaluate an avian radar systems performance in varying weather conditions, changing bird populations due to migration and varying clutter conditions. The validation work was performed at Naval Air Station Whidbey Island (NASWI), Washington, in cooperation with the US Navy BASH program, due to the large resident bird population and seasonally changing bird populations along the Pacific Flyway. A Furuno X-band, 25kW, marine radar outfitted with a Furuno 22 degree array antenna was the primary sensor which fed raw radar data to an Accipiter digital processing system. A similar field methodology was utilized at DFW where a GMI radar unit and the BSTAR v3 unit from SRC were deployed. At other radar deployments such as at ORD and JFK, opportunistic observations and observations during point count surveys were utilized for validation.