Just to set the record straight.... I spent almost two years working with Transport Canada writing five chapters and editing a comprehensive safety publication on bird strikes titled "Sharing the Skies" and high altitude bird strikes do occur!
The evidence is well documented from a number of reliable sources. There is extensive radar evidence of bird movements at altitudes above 30,000 ft. in certain parts of the world. These high altitude strikes do not occur frequently, but are not unknown.
The area to pay attention to with respect to bird strike risk is operations at 10,000 ft. and below, particularly during migratory bird seasons. With increasing migartory bird populations and mean weights coupled with the current airframe and engine certification standards we all need to take care when conducting high speed operations (>250knots) below 10,000 ft. Hitting an 8 lb goose at 280 IAS at 5,000 feet can exceed the certified impact force on many aircraft.
Just something to think about during the autumn season......