This video shows the damage that can be inflicted on an aeroplane from a birdstrike.  In this clip the aeroplane hits a single bird rupturing the starboard undercarriage strut and punching a hole into the tail fin.

http://www.redbullairrace.com/cs/Satellite/en_air/Video/Archs-Bird-Strike-In-San-Diego-2009-021238615428145?p=1238611393596

The pilot, 42 year old Hannes Arch, is currently leading the 2009 championships, one point ahead of his rival the Brit Paul Bonhomme.