Joe...you sure they are frozen?
I thought that it was a thawed bird... otherwise its like throwing a solid block of ice at the windshield.....
http://www.sae.org/aeromag/techupdate_3-00/05.htm
http://www.tc.gc.ca/CivilAviation/Aerodrome/WildlifeControl/TP13549/Chapter12/Chapter12d.htm