hi there
Spares are fitted as often as required, the same as for any other aircraft. Some parts such as pumps, motors, etc have lives limited by hours or cycles and are changed accordingly.Other parts are changed when they wear out such as obvious stuff like tyres, bulbs, seals,etc.Air Corps aircraft operate to maintenance schedules exactly like their civil counterparts.
Bird strikes are a regular event in all air forces and airlines and nine times out of ten, very little damage is caused.Bird strikes only make the news when they cause serious damage.
regards
GttC